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COPYRIGHT DEPOSIT. 



ELEMEiNTS 



INORGANIC CHEMISTRY 



DESCRIPTIVE AND QUALITATIVE 



BY 
JAMES H. SHEPARD 

Professor of Chemistry, South Dakota Agricultural College 
and Chemist for the Experiment Station 



REVISED EBTITON' 



BOSTON, U.SA. 

D. C. HEATH & CO., PUBLISHERS 

1904 



LIBRARY of CONGRESS 
Two Copies Received 
APR 21 1904 

Copyright Entry 

CLASS *^XXc. No. 

SJTO / O 
COPY B 



Entered according to Act of Congress, in the year 1885, by 

JAMES H. SHEPAKD, 
in the Office of the Librarian of Congress, at Washington. 

Entered according to Act of Congress, in the year 1904, by 

JAMES H. SHEPARD, 
in the Office of the Librarian of Congress, at Washington. 



•v* •*'• 



PKEFAOE, 



Thts elementary treatise is based upon plans and 
methods which have been employed in the author's 
laboratory throughout a series of years, and no work has 
been incorporated in the text or in the exercises that 
has not there been proven practicable. 

A love for the science of chemistry would have for- 
bidden any attempt to add another text-book to the 
already too extended list of Elementary Chemistries had 
not the hearty commendations of teachers of national 
reputation and undoubted ability encouraged both the 
author and the publisher to put this work in permanent 
form. 

During the correspondence which grew out of the 
issue of this work, it has become evident that many 
of the best teachers in all sections of the country are 
pursuing independently a plan essentially the same ; and 
the deepest regret which the author feels in seeing the 
work go to press arises from the fact that it signals 
for the close of his correspondence and labors with such 
an enthusiastic corps of fellow-workers. If it shall be 



IV PREFACE. 

found that this work, towards which they have contrib- 
uted so freely, meets with their hearty commendations, 
he will rest satisfied with his labor of love. 

It now only remains to return thanks to those who, so 
patiently and ofttimes so laboriously, have assisted the 
author in completing this work. 

Dr. Ira Remsen, Professor of Chemistry in Johns 
Hopkins University, has critically read the work in man- 
uscript and in proof, and has contributed much toward 
the accuracy and the arrangement of the topics treated, 
particularly those which pertain to chemical theories. 

The following well-known and enthusiastic teachers of 
chemistry have read the work in proof, and have given the 
author constant advice as, from time to time, the sheets 
appeared : — 

Otis Coe Johnson, Assistant Professor of Applied Chem- 
istry, University of Mich. ; Robt. B. Warder, Professor of 
Chemistry, Purdue University, and State Chemist of Ind. ; 
W. W. Daniells, Professor of Chemistry, University of 
Wis. ; Jas. A. Dodge, Professor of Chemistry, University 
of Minn.; E. J. Bartlett, Professor of Chemistry, Dart- 
mouth College ; Delos Fall, Professor of Natural Science, 
Albion College ; Albert C. Hale, Instructor in Chemis- 
try, Central Grammar School, Brooklyn, N.Y. ; George 
Weitbrecht, Chemist and Instructor Natural Science, 
High School, St. Paul, Minn. ; Leroy Griffin, Professor 
of Natural Sciences, Lake Forest University, 111. ; Herbert 
C. Foote, Chemist and Instructor Natural Science, High 



PREFACE. V 

School, Cleveland, O. ; and many other teachers of Chem- 
istry in preparatory, normal, and collegiate departments. 

Article 234 on the Natural Classification of the Elements 
is due to the kindness of Professor Warder. 

The author is aware that many data, not usually given 
in works for beginners, appear in the text ; but, in the 
laboratory, these will be found to be useful and valuable 
additions. 

It has been the constant aim, in preparing this book, to 
make the labors of the teacher as light as possible, and to 
place the laboratory work where it would do the most 
good, in the hands of the students. 

» 

NOTE FOE THE KEVISED EDITION. 

The author gladly avails himself of the opportunity 

offered by the issue of this revised edition to make such 

changes in data as exact research seems to warrant, and 

also make such additions as will bring the text up to 

date. The renewed interest in theories concerning the 

constitution of matter has not been productive of results 

sufficiently established to warrant introduction into a 

working text at this time. 

J. H. S. 

March 1, 1904. 



TO THE TEACHER 



Methods. 



It is with no little diffidence that the author approaches the 
subject of Methods. He is fully aware that every teacher has 
his own method, and that all successful methods are entitled to 
respectful consideration. There are, however, some principles 
upon which all are agreed, and a classification and a brief dis- 
cussion of the different methods which have been employed may 
at least prove suggestive. 

The problems before us are these : — 

1. If we teach chemistry at all, what advantages has this 
science to offer as factors in developing the youthful mind, and 
what good results will follow its study ? 

2. If the study of chemistry be positively desirable, what 
method of presentation will best accomplish the desired results ? 

1. Neglecting for the present the claims of those who would 
become chemists by profession, let us consider chemistry as 
a means of education. In this capacity, when properly taught, 
chemistry awakens and cultivates a spirit of investigation ; it 
encourages the student to ask Nature questions, and it is unex- 
celled by any other branch of learning in the clearness and con- 
clusiveness of the answers received ; it insists upon the strictest 
habits of observation ; it leads to the concentration of thought 
and of energy ; it educates the senses ; it trains the hand to 
delicate manipulation ; it exercises the faculty of reason and 
the power of judging ; it affords useful information peculiarly 



viii TO THE TEACHER. 

its own, and thus forms an important part of a good, general 
education. 

Backed by such advantages as these, it really seems that 
chemistry should be deemed worthy of a place in all liberal as 
well as in purely scientific education. 

2. When it comes to methods of instruction, the teacher has 
many from which to choose. These methods may be arranged 
approximately under four general divisions : — 

(1) The Classical or Didactic method. 

(2) The Laboratory method, in which the teacher does all the 
experimentation in the presence of the class, and accompanies 
the experimentation by didactic instruction. 

(3) The Working- Laboratory method, in which the student 
does his own experimentation, and receives little or no 
didactic instruction. This method varies somewhat, in its 
application : — 

(a) The student may be required to work with no aid from 
text-books, etc., relying upon his work alone for the benefits 
to be obtained, the instructor in this case acting really as a 
demonstrator. 

(b) The student may have a text-book as a guide, the in- 
structor acting as before. 

(4) A method which the author begs leave to christen the 
scientific method ; this embodies all the good features of the 
preceding methods. 

The experience of many careful instructors would warrant the 
following estimate of the relative value of these methods : — 

The first method affords some special information ; otherwise, 
chemistry, when thus taught, is equalled as an educational factor, 
by history, and b} T kindred subjects ; and is excelled by mathe- 
matics and the classics. 

The second method accomplishes as much as the first, and to 
a very limited extent cultivates observation ; farther than this, 
no advantages are to be gained by its use. 

The third method incites to investigation ; trains the senses to 



TO THE TEACHER. XX 

observe ; trains the hand to careful manipulation ; and encour- 
ages the student to originate. But (a) is too slow ; it requires 
more time than can be devoted to this study ; and although the 
student may "know well what little he does know," his rea- 
soning powers are not developed, and his fund of information is 
not sufficiently increased, (b) accomplishes its ends somewhat 
more rapidly than (a) , and consequently yields more informa- 
tion in a given length of time ; otherwise, it 4s not better than 
(a). As a rule, students taught by the third method are very 
weak in chemical theory. 

An insight into the fourth method may best be obtained by 
a description of the manner of its application. This method 
contemplates : didactic instruction by the teacher ; a good text- 
book, and as many books of reference as possible ; much work 
by the student, who should keep a careful record of all work 
done, and who should recite frequently ; and work by the 
teacher, either in the presence of the class where the class is 
large, or personal directions to the student when the class is 
small. 

The use of this method is extremely simple. The teacher 
assigns a lesson from the text, indicating such parallel reading 
as the time at the student's disposal may permit ; he then goes 
over the lesson, and gives such working directions and cautions 
as the subject and the student's capabilities may demand, thus, 
in most cases at least, saving the student from wasting his time 
in repeating the useless blunders of those who worked centuries 
ago ; if the experiments be dangerous, or if the line of work be 
new, the teacher either makes the experiment for the class with 
little or no explanation, or he explains the general principles, 
leaving the student, when safety permits, to work out the 
details ; after this, the student is sent to his desk, where he 
works, reads, and makes his notes for the next recitation. 

The following day the student is questioned concerning his 
work, and is encouraged to tell truthfully and exactly how he 
succeeded, if he has succeeded, or why he failed, if he has failed. 



X TO THE TEACHER. 

In case the student has failed, and does not know the reason, 
or gwes the wrong reason, the teacher, meanwhile explaining 
nothing himself, calls upon other members of the class until the 
point in question is elucidated. If all have failed, which rarely 
happens, the teacher gives directions anew, and the students try 
again. In general, the teacher aims to do as little work for 
the class as possible, and to tell the student nothing that he can 
find out for himself in a reasonable length of time. 

Reviews and those topics which are necessary to the science 
as a whole, and which are not covered by the student's work, 
are faithfully taught by didactic methods. 

Variety is introduced and practical results are obtained in 
several ways, and thus the student's interest is never permitted 
to flag. Students are assigned essays upon various topics ; 
are given unknown substances to analyze ; are required to make 
analyses of substances with which they are familiar, such as 
coins, worn-out articles of jewelry, alloys, common salt, baking- 
powder, samples of drinking-water, crude drugs from the drug 
store, etc., etc. 

In keeping his notes, the student constantly recognizes the 
fact that the knowledge he is seeking is to be drawn from 
phenomena observed while working with known factors. A 
good form for the headings of a note-book is as follows : — 

1. Required Conditions, 

2. Known Conditions. 

3. Operations. 

4. Conclusions. 

Under 1 the student enumerates what he wishes to, know; 
under 2 he enumerates his working materials ; under 3 he tells 
what he does ; and under 4 what conclusions he has reached. 

In making his notes, the student is warned that he may err": 
(1) by taking a trivial required condition; (2) by assuming a 
required condition that will not follow from the premises ; 
(3) by an indefinite or obscure description of his operations ; 
'4) by reaching a conclusion more general than the premises 



TO THE TEACHER. XI 

warrant ; and (5) by employing bad English in any of the pre- 
ceding divisions. 

In this book, written with special reference to the fourth 
method, the student's work, so far as practicable, is not fore- 
stalled by telling him what phenomena are to occur, and many 
queries are left to be answered by an experiment which the 
student may devise. In the closing portions of the book, all 
experiments (as such) are purposely omitted with the sugges- 
tion that, as the student is no longer, in the strict sense of the 
word, a beginner, he should be thrown still farther upon his 
own resources. He is asked to prepare various salts and com- 
pounds of the metals, and to describe their preparation as 
experiments ; this is work well adapted to afford an exercise 
more exacting than anything previously attempted. Another 
good exercise for the student is to prepare working solutions for 
himself and his classmates, starting with the crude materials. 

By this method, the student will not only secure a lasting 
benefit from chemistry, as an educator of hand and mind, but 
in case he so desires, he will find himself amply prepared for 
further pursuing this delightful study. 

n. 

What should the Student memorize? 

As in all other studies, this question is frequently asked con- 
cerning chemistry. In the curriculum of all schools in which 
chemistry is taught to beginners other studies are found, or 
should be found, which are peculiarly adapted to cultivate the 
faculty of memory ; the amount of memorizing required in 
chemistry should be quite limited, depending more or less upon 
the curriculum itself. 

In general, it is safe to say that much valuable time has been 
frittered away by requiring the student to memorize unimportant 
details which not even an expert retains. Because certain facts 



Xll TO THE TEACHER. 

or numerical data are given in a text, it does not follow that the 
student's memory must be burdened with them ; there are other 
uses for such data, and especially so in a working text. Thus, 
for example, the weight of one litre of a gas, atomic heats, 
specific gravities, densities, etc., etc., may be ' utilized in 
solving problems. 

It is not even necessary to memorize the atomic weights or 
such units as the weight of one litre of hydrogen, since the stu- 
dent will learn these data by frequently using them, just as we 
all have learned the multiplication table. It is, however, a 
positive advantage to have these data given in the body of the 
text, since a frequent reference to them serves in a certain way 
as a review. 

Again, the author has never required his classes to memorize 
tests and separations, and still his students, by way of final 
work, have been able correctly to analyze complex unknown solu- 
tions without the aid of reference books or of text-books ; this 
was accomplished by simply giving the student much work to 
do, and then by asking him to explain his work. And again, it 
would be manifestly absurd to require the student to memorize 
the language of the text in experiments. And finally it should 
suffice to bear in mind that to be able to do, to reason, to origi- 
nate, is far better than to be able to repeat from memory things 
not half understood. 

m. 

A Briefer Course. 

For various reasons some teachers may wish to use certain 
portions of the text and to omit the rest. There is no reason 
why this may not be done. Experience has shown that, in 
a working text, even of the most elementary character, it is 
desirable to have the book quite complete, thus lightening the 
labor of the teacher, and providing for emergencies which often 



TO THE TEACHER. Xlll 

and unexpectedly arise. For example, one piece of apparatus 
may be broken, or it may be wanting, while another, which 
mav be made to answer the same purpose, is available ; or, a 
student in his work may come upon something which not eyen 
the teacher could foresee ; one chemical may have been entirely 
consumed, while another, which will answer, may still be plenti- 
ful, etc.. etc. In yiew of all these considerations, it is evident 
that a somewhat full text will be more satisfactory to both 
student and teacher, eyen though certain portions of it are 
omitted, or dwelt upon quite lightly. There is no truth in the 
tradition that " to omit certain parts of a book causes the 
student to be less thorough " ; on the contrary, such a process 
should teach him to select what he really wants from what he 
does not want, — a lesson he must learn sooner or later. There 
is one thing, at least, that a full text certainly does do, and that 
is, it forever banishes from the student's mind the idea that he 
has learned all there is to know of chemistry. 

The following hints may serve to show how the work ma}* be 
lessened or how the course may be shortened : — 

1. Omit the experiments marked op. 

2. AVhen two or more experiments tend toward the same 
general result, omit as many as desirable, selecting those most 
readily performed by the apparatus and working material 
available. 

3. Omit the rarer elements and their compounds. 

4. In the compounds of the common elements, dwell at length 
upon the most useful ones, e.£/., in the compounds of nitrogen, 
place the stronger work upon ammonia, nitrogen monoxide, and 
nitric acid, omitting or dwelling but briefly upon the remaining 
compounds. 

5. The qualitative work may be curtailed by omitting some 
of the separations, etc. 

6. Sometimes, also, the teacher may prefer to modif} T the 
order of presenting the various topics ; for example, he may 
wish to discuss molecules more thoroughly at the outset, or he 



XIV TO THE TEACHER. 

may wish the class to experiment with the oxides of nitrogen 
before discussing them in their bearing upon the law of multiple 
proportions, etc., etc. In this way he may conform to his own 
ideas of presentation 



CCOTTEWTS. 



HISTORICAL SKETCH. 

PAGE. 

The Ancients. ■ — The Arabs. — Alchemy of the Middle Ages. 

— Medical Chemistry. — Pneumatic Chemistry. — Modern 
Chemistry 1-7 

INTRODUCTION. 

Experimentation. — Elements. — Compounds. — Chemistry 
Defined. — Three Forms of Matter. — Chemism. — Laws of 
Definite and Multiple Proportions. — Combining Number. 

— Atomic Theory. — Atomic Weight. — Determination of 
Atomic Weight. — Names of the Elements. — Symbols. — 

A Table of the Elements 8-22 

CHAPTER I. 

Oxygen: its occurrence, preparation, properties, and tests. — 
The Bunsen Burner and the Blow-pipe. — Ozone : prepara- 
tion, properties, and tests . 23-33 

CHAPTER II. 

Hydrogen: its occurrence, etc. — Water: its occurrence, etc. 

— Composition of Water. — The Oxy-hydrogen Blow-pipe. — 
Impurities in Drinking-water, and Tests for. — Hydrogen 
Dioxide : its preparation, etc ... 34-49 

CHAPTER HI. 

Nitrogen : its occurrence, etc. — Ammonia : its occurrence, 
etc. — Nitrogen Monoxide : its occurrence, etc. — Nitrogen 



XVi CONTENTS. 

PAGE; 

Dioxide. — Nitrogen Trioxide. — Nitrogen Tetroxide. — 
Nitrogen Pentoxide. — The Nitrogen Acids: Hyponitrous, 
Nitrous, and Nitric Acids. — Hydroxylamine. — Estimation 
of Ammonia in Drinking-water . • . . 50-7£ 

CHAPTER IV. 

Binary Compounds. — Acids. — Bases. — Salts. — Acid and 

Normal Salts. — Writing Equations . . . . .. . . . 73-83 

CHAPTER V. 

The Atmosphere. — Atmospheric Pressure. — Measurement of 
the Temperature of the Atmosphere. — Impurities in the 
Atmosphere. — Determination of the Volumes of Oxygen and 
Nitrogen in the Atmosphere. — Effects of Heat and Pressure 
on the Volume of a Gas. — Weight and Density of Gases. — 
Useful Problems 82-9J 

CHAPTER VL 

Chlorine : its occurrence, etc. — Hydrochloric Acid : its 
preparation, etc. — Oxides of Chlorine: Monoxide, Trioxide, 
Tetroxide ; their preparation, etc. — The Chlorine Oxacids : 
Hypochlorous, Chlorous,, Chloric, and Perchloric Acids, and 
their preparation, etc. — Estimation of Chlorine in Drinking- 
water ... 92-107 

CHAPTER VH. 

Bromine : its occurrence, etc. — Hydrobromic Acid : its prepara- 
tion, etc. — Hypobromous, Bromous, and Perbromic Acids, 
and their preparation, etc . . * . 108-114 

CHAPTER VIH. 

Iodine and Fluorine. — Occurrence, etc., of Iodine. — Hydri- 
odic Acid : its preparation, etc. — Iodic and Periodic 
Acids, and their preparation, etc. — Fluorine. — Hydrofluoric 
Acid .,..,,,.,... 115-124 



CONTENTS. XV11 

CHAPTER IX. 

PAGE. 

Carbon : its occurrence, etc. — Methane. — Ethylene. — Acety- 
lene. — Illuminating Gas. — Carbon Monoxide. — Carbon 
Dioxide. — The Carbonates. — Cyanogen. — Prussic Acid. — 
Estimation of Carbon Dioxide in Living-rooms . . . 125-148 

CHAPTER X. 

Molecules. — Avogadro's Hypothesis and the Computation of 
Molecular Weights. — Determination of Atomic Weights by 
Means of Avogadro's Hypothesis. — Valence. — Substituting 
Power and Valence . ... 149-156 

CHAPTER XI. 

Sulphur : its occurrence, etc. — Hydrogen Sulphide. — Hydro- 
gen Per-sulphide. — Sulphur Dioxide. — Sulphur Trioxide. 

— Sulphurous Acid. — Sulphuric Acid. — JSordhausen, or 
Fuming Sulphuric Acid. — Thiosulphuric Acid and the 
Thiosulphates. — Carbon Bisulphide. — Selenium : its occur- 
rence, etc. — Tellurium : its occurrence, etc. . . . 157-183 

CHAPTER XIL 
Silicon and Boron. — Occurrence, etc., of Silicon. — Silica. — 
The Silicon Oxacids and the Silicates. — Other Compounds 
of Silicon. — Occurrence, etc., of Boron. — Boron Com- 
pounds, etc 184-192 

CHAPTER XIII. 
Phosphorus : its occurrence, etc. — Phosphorus and Hydrogen. 

— Phosphorus Oxides. — Phosphorus Oxacids : Hypophos- 
phorus Acid, Phosphorous Acid, Phosphoric Acid, Meta- 
phosphoric Acid, Pyrophosphoric Acid. — Examination of 
Unknown Substances for the Acids previously given . . 193-207 

CHAPTER XIV. 
Introduction to the Metals. — Properties. — Alloys. — 
Analytical Classification of the Metals. — Salts of the Metals. 
i— A Natural Classification of the Elements 20&- 223 



XVUl CONTENTS. 

CHAPTER XV. 

PAGE, 

The First Group Metals. — Lead, and its occurrence, prep- 
aration, properties, uses, compounds, and tests. — Silver: its 
occurrence, preparation, etc. — Mercury : its occurrence, etc. 
— Separation and Identification of Lead, Silver, and 
Mercury 224-240 

CHAPTER XVI. 

The Second Group Metals. — Arsenic, and its occurrence, 

preparation, properties, uses, compounds, and tests. — Anti- 
mony : its occurrence, etc. — Tin ; its occurrence, etc. — Sepa- 
ration and Identification of Arsenic, Antimony, and Tin. — 
Bismuth : its occurrence, etc. — Copper : its occurrence, etc. — 
Cadmium: its occurrence, etc. — Separation and Identification 
of Bismuth, Copper, and Cadmium. ■ — Separation, etc., of 
the Metals of the Second Group. — Separation of the Metals 
of Groups I. and II. — The Rare Metals of the Second 
Group: Gold, Platinum, Palladium, Ruthenium, Iridium, 
Rhodium, Osmium, Tungsten, Molybdenum ..>... 241-272 

CHAPTER XVII. 

The Third Group Metals. — Iron : its occurrence. — Iron 
Ore. — Preparation of Iron. — The Iron Furnace. — Wrought 
Iron. — Steel. — Properties, Uses, and Compounds of Iron. — 
Tests for Iron. — Chromium : its occurrence, etc. — Tests for 
Chromium. — Aluminum : its occurrence, etc. — Tests for Alu- 
minum. — Separation and Identification of Iron, Chromium, 
and Aluminum. — Nickel : its occurrence, etc. — Tests for 
Mckel. — Cobalt : its occurrence, etc. — Tests for Cobalt. — 
Separation and Identification of Mckel and Cobalt. — Man- 
ganese : its occurrence, etc. — Tests for Manganese. — Zinc : 
its occurrence, etc — Separation and Identification of Nickel, 
Cobalt, Manganese, and Zinc. — The Rare Metals of the 
Third Group : Beryllium, Indium, Gallium, Yttrium, Lan- 
thanum, Cerium, Didymium, Terbium, Erbium, Thorium, 
Titanium, Zirconium, Uranium, Tantalum, Niobium, and 
Vanadium . . 273-308 



CONTENTS. XIX 

CHAPTER XVIII. 

PAGE. 

The Fourth Group Metals. — Barium : its occurrence, etc. — 
Tests for Barium. — Strontium : its occurrence, etc. — Tests 
for Strontium. — Calcium : its occurrence, etc. — Tests for 
Calcium. — Separation and Identification of Barium, Stron- 
tium, and Magnesium. — Magnesium : its occurrence, etc. — 
Tests for Magnesium 309-319 

CHAPTER XIX. 

The Fifth Group Metals. — Potassium : its occurrence, etc. — 
Tests for Potassium. — Sodium: its occurrence, etc. — Soda 
Preparation by the Black Ash and Ammonia Processes. — 
Tests for Sodium. — Ammonium. — The Ammonium Salts. 
— The Analysis of Unknown Substances . . ... 320-340 

APPENDIX. 

Devoted to The Laboratory, Apparatus, Working Material, 

Reagents, etc., etc. , 341-366 



HISTOEICAL SKETCH. 



1. The word Chemistry is probably derived from Che- 
mia, which is an old name for Egypt. The word signifies 
simply the Egyptian art; and it was so called since chem- 
istry was first practised by the Egyptians. 

Like all sciences which have to deal with Nature, 
chemistry has been developed by a long and tedious 
series of experiments. Since the art of experimenting 
is a comparatively modern one, the Ancients, as one 
would naturally infer, were not deeply versed in this 
science. The principal obstacle in the way of their prog- 
ress is apparent when we know that they made great use 
of the speculative method ; that is, when they wanted an 
explanation of any fact in Nature, they simply thought 
about it, without seeking to verify their conclusions by 
the test of rigid experiment. 

The Egyptian priests were the learned class of their 
time ; and their researches were carried on with such an 
air of mystery, and at such uncanny times, and in such 
secret places, that Chemistry was spoken of as the Black, 
or Secret Art. We find, however, that the Egyptians 
possessed a considerable knowledge of the arts of dye- 
ing, painting, and glass-making ; and that they were quite 
skilled in metallurgy and the manufacture of pottery. 

About the time of Aristotle (fourth century B.C.) it was 



2 HISTORICAL SKETCH. 

believed by some that all bodies are only modifications of 
one fundamental substance ; by others, that all substances 
are but the dwelling-places of four properties, — viz., heat, 
cold, moisture, and dryness, — and that these four prop- 
erties of matter are best represented in the four sub- 
stances, fire, air, water, and earth. It was further believed 
that these properties could be transferred from one body 
to another, and, as a consequence, that the ordinary metals, 
such as iron, could be transformed into the noble metal, 
gold. It will be readily understood that this thought fur- 
nished a powerful incentive to work, which incidentally 
contributed something towards the advancement of chem- 
istry. Considering the object he had in view, it is not 
surprising that the chemist practised his art in caverns 
and at night, where no prying eyes could see his opera- 
tions, nor that he recorded his transactions in ambiguous 
terms and in mysterious characters. 

We thus find the ancients making but little progress in 
true chemical science. Moreover, we now know that their 
pernicious methods and theories were detrimental for many 
centuries afterwards, notwithstanding the fact that chem- 
istry originated in these self-same theories and methods. 

2. The Arabs, in the year 640 A.D., invaded Egypt and 
became acquainted with the Egyptian sciences. 

Geber, an Arabian alchemist of the eighth century (the 
Arabs gave chemistry the name Al-Chemia), wrote several 
books on chemistry. He understood many chemical manip- 
ulations, discovered a solvent for gold, a mixture of nitric 
and hydrochloric acids or aqua regia, and proposed the first 
theory of the chemical composition of the metals, viz., that 
sulphur and mercury were the simple or primary sub- 
stances from which all the different metals are derived. 



HISTORICAL SKETCH. 3 

In this period, then, we find an encouraging advance ; 
chemical processes are becoming more generally known, 
and a suggestive though erroneous theory is announced, 
which is destined to develop, through many modifications, 
from error into truth. As an instance of the manner in 
which this theory was afterwards modified and extended, 
we may here mention the fact that Basil Valentine of the 
fourteenth century, accepting sulphur and mercury as 
the primal elements, extended the conception to all sub- 
stances ; and that Boyle, three centuries later, doubtlessly 
influenced by this same theory to investigate this problem, 
announced the true solution. 

3. During the Middle Ages the Arabians fostered the 
sciences. Their academies in Spain were sought by stu- 
dents from all parts of the civilized world ; these philoso- 
phers, returning to their native countries, taught chemistry 
there. Thus we find, in the thirteenth century, Raymond 
Lully in Spain, Albertus Magnus in Germany, Arnold 
Villanovanus in France, and Roger Bacon in England. 
All these believed in the transmutation of the metals, and 
the philosophy of their time teemed with mysticism and 
nonsense. We must here note that the all-absorbing theme 
was the Philosopher's Stone, a substance which should 
transform the baser metals into precious gold. The 
writings of this period are extravagant, confused, and 
purposely so written that they are nearly unintelligible 
Bacon, however, to clear himself of the charge of sorcery 
(chemistry was still the Black Art), wrote a treatise in 
which he showed that many things supposed to be caused 
by supernatural agencies are produced by natural causes. 

The search for the Philosopher's Stone during this 
period brought to light many facts in inorganic chem- 



4 HISTORICAL SKETCH. 

istry; and thus do we find alchemy slowly but surely 
paving the way for genuine chemistry. 

4. In the era of Medical Chemistry, chemists directed 
their investigations into different medicines. They also 
sought the Elixir Vitae, or Elixir of Life, — a cordial 
which should cure all the ills of mankind, and give per- 
petual youth. By a strange misinterpretation of Aristotle, 
some chemists also conceived the idea that the Philoso- 
pher's Stone, when found, would achieve the same results. 

Paracelsus (1493-1541) was the most noted of these 
investigators. By his great achievements he earned the 
title, The Father of Medicine. 

Agricola (1490-1555) wrote the first treatise on Metal- 
lurgy and Mining. 

Libavius wrote the first Hancl-Book of Chemistry, his 
Alchemia, which was published in 1595. 

Van Helmont (1577-1644) deserves special mention, 
since he was the first to emancipate himself from the 
theories of the Aristotelian school. He also discovered 
various gases, and showed that metals are not destroyed 
when dissolved in acids. But he, too, had his delusion: it 
was his Alkahest, a universal solvent as well as a universal 
medicine. 

Robert Boyle (1627-1691) advanced still further: he 
claimed that the exact number of the elements was not 
known, and he clearly stated the difference between the 
elements and the compound substances. He also raised 
chemistry to the dignity of a true science, which was not 
to be studied as a part of any other, but as one of the 
great Natural Sciences. 

During this period many useful and potent medicines 
were discovered, and, although error was by no means 



HISTORICAL SKETCH. 5 

completely banished, the fundamental principles of chem- 
istry were well grounded in truth. Hereafter, the history 
of chemistry is a history of improvements, discoveries, 
and researches extending to all the different branches 
into which this science has developed. 

5. Pneumatic Chemistry was the next phase in the 
development of our science. This period was remarkable 
for the investigation of the properties of gases, and the 
phenomena of combustion. 

Stahl sought to explain combustion by assuming the 
existence of a combustible principle, or element, which he 
termed Phlogiston. According to his views, this element 
must be taken away from combustible bodies to render 
them incombustible. 

Among the believers in Phlogiston were three remarka- 
ble men : — 

1. Joseph Priestley, who discovered oxygen gas in 1774, 
and afterwards other and important gases. 

2. Henry Cavendish (1731-1810), who experimented 
with inflammable air (hydrogen gas), determined the 
density of the gases, and discovered the unvarying com- 
position of the atmosphere. 

3. Charles William Scheele (1742-1786), a Swedish 
chemist, who discovered chlorine gas, prussic acid, gly- 
cerine, and the pigment, Scheele's green. He also made 
such other researches that he is entitled to be placed 
among the founders of Quantitative Analysis. 

None of these three ever discovered the true explana- 
tion of combustion. The Phlogiston theory, however, 
could not stand the test of rigid experiment ; and Lavoi- 
sier, by exposing its fallacies, ushered in the new era of 
chemistry, or 



6 HISTORICAL SKETCH. 

6. The Modern Era. — From his own experiments and 
those of Ins predecessors, Lavoisier determined that a burn- 
ing body unites with, or takes up a combustible element, 
oxygen. By the use of the balance he discovered the 
great fundamental truth, that, however great the changes 
matter may undergo, no loss in weight occurs, or, in other 
words, that matter is indestructible. He also introduced 
a system of chemical nomenclature, which has been of 
inestimable value, as chemists not only disagreed as to the 
names of the substances with which they were acquainted, 
but often and purposely called one substance by so many 
names that their meaning was not at all certain. 

Dalton, next to Lavoisier, gave a great impetus to the 
study of chemical phenomena by the discovery of the laws 
of combination, known as the laws of " definite and mul- 
tiple proportions^" and by the propounding of the atomic 
theory. 

Gay Lussac discovered the law of combination of gases 
by volume. 

In 1808 Sir Humphry Davy discovered, by means of 
electrolysis, the compound nature of the alkalies. 

In 1828 Wohier prepared urea from inorganic sub- 
stances, thus crossing out the division line between or- 
ganic and mineral chemistry. 

Spectrum analysis, dating back scarcely farther than 
1860, has not only revealed the existence of many new 
terrestrial elements, — such as caesium, thallium, rubi- 
dium, indium, etc., — but has enabled us to determine 
the composition of the sun and stars themselves. 

Chemistry is no longer the Black Art, nor the handmaid 
of astrology, but a legitimate science, exact in its methods, 
and beneficent in its results. While, as a pure science, its 



HISTORICAL SKETCH. 7 

aim is the investigation of truth, it has in its practical 
application formed an important factor in the industries 
of all civilized countries. 

Suggestion. Read RodwelPs Birth of Chemistry ; Roscoe's Spectrum 
Analysis; WhewelFs History of the Inductive Sciences, pp. 261-310; 
Roscoe and Schorlenimer's Treatise, pp. 1-40- Write short biographical 
sketches of the chemists mentioned (consult an Encyclopedia). 

During the last decade the most notable advances in 
chemical knowledge have been made along physico-chem- 
ical lines. Van 't Hoff and Arrhenius have given us 
practical theories of solution and electrolytic dissocia- 
tion ; and the period has witnessed a vast addition to our 
knowledge of chemical compounds. Methods of deter- 
mining the molecular weights of compounds not readily 
vaporized, re-determinations of the atomic weights, and a 
systematic research into the domains of chemical dynamics 
and of thermo-chemical relations are all tending to enhance 
the claims of chemistry as an exact science. (See trea- 
tises of Ostwald and Nearnst (Macmillan).) 

The years 1902-1903 have seen extensive investigations 
of the radio-activity of self-luminous bodies, such as the 
compounds of uranium, thorium, radium, etc. Many the- 
ories are advanced to explain these phenomena. Two 
noteworthy ones are : 1st, that radio-active substances act 
simply as transformers of the obscure forms of radiant 
energy existing everywhere ; 2d, that the atoms of such 
substances are undergoing dissolution, while the simpler 
particles produced rearrange themselves into atoms of 
other elements. Thus it is possible that radium atoms 
are flinging off particles which recombine to form helium 
atoms. Either theory would account for radiant energy. 
Read Mine. Curie's thesis on " Radio-active Substances," 
Chem. News, Aug. 21 to Deq. 1, 1903. Also see page 308. 



INTRODUCTION, 

DEFINITIONS. — LAWS OF COMBINATION IN DEFINITE AND 
MULTIPLE PROPORTIONS. — ATOMIC THEORY. — ATOMIC 

WEIGHTS. — NAMES OF ELEMENTS. — SYMBOLS. TABLE 

OF THE ELEMENTS. 

7, To Experiment with a substance is to place it 
under certain conditions or with certain substances to 
ascertain its properties and behavior. 

An experiment is a question intelligently put to 
Nature. 

Experiment 1 p. (To the student.) Since this is your 
first experiment in chemistry, you may feel uncertain as to 
what you are expected to do, or how you are to derive the 
most benefit from your work. In general, it is a safe poiic} 7 
always to work carefully, and to note all phenomena that 
occur ; from these phenomena you are then expected to derive 
certain desired conclusions. It is true, that, for various rea- 
sons, you may sometimes need assistance in reaching these 
conclusions ; in such cases you must necessarily rely upon the 
experience of others. Although this latter method is a legiti- 
mate and often an indispensable way of obtaining knowledge, 
we may safely say that he has the most truly scientific spirit 
and methods, who, so far as possible, works and observes for 
himself. 

In the experiments 3-011 are about to make, you may watch 
for any changes that take place in the substances experimented 
upon. Some of these changes may be perceptible to the sense 



INTRODUCTION. 9 

of sight, and some to the sense of smell ; others may be per- 
ceptible to the sense of touch ; and still others to general sensi- 
bility ; but, as a usual thing, the chemist depends mainly upon 
sight and smell co detect any changes in the substances upon 
which he is tvorking. Now let us ask of Nature a few ques- 
tions. 

Steadily and persistently hold a platinum wire in a Bun sen 
flame (Art. 28). What occurs? Now cut off a very short 
piece (say 2 mm ) of the wire, place it upon a piece of charcoal, 
and heat it by means of the blow-pipe flame (Art. 28). What 
takes place? Then cover the bit of wire with a mixture of 
sodium carbonate (Na 2 C0 3 ) and potassium nitrate (KN0 3 ), 
and slightly moisten the whole. Again heat in the blow-pipe 
flame as before. What results? Now wash the piece of wire 
clean, and place it in a test-tube ; then add nitric acid (HN0 3 ) , 
and warm gently in the Bunsen flame. What occurs? Again 
wash the wire, add Irydrochloric acid (HC1), and warm as 
before. What have you observed? You may possibly be 
inclined to answer, " Nothing of importance." But let us 
see. Did you succeed in separating the platinum into two or 
more different substances f Assuredly not ; nor could you have 
so separated it by any process known to man. Now that is 
important, since there are, besides platinum, about sixty- eight 
other substances that have not been separated into simpler 
ones : and these should have a class name. Hence the fol- 
lowing name and definition : — 

8. An Element is a substance that has not been divided 
into two or more simpler substances. 

Examples. Gold, Iron, Silver, Tin, Oxygen, Potassium. 

Note (to the student). You are not to infer that all these sixty-eight 
elements would behave precisely like platinum : such, indeed, is not t-he 
case. Very few of them could have withstood the above treatment with- 
out undergoing marked changes. None of them, however, would have 
yielded two different substances, in which respect alone do they all agree 
with platinum, 



10 INTRODUCTION. 

Query. What is a definition ? 

Suggestion. Try, as above, bits of lead, copper, iron, zinc, etc. Com- 
pare the results with those obtained from platinum. 

Exp. 2 p. Place in a test-tube a short piece of thoroughly 
dried pine wood as thick as a lead-pencil. Heat it over a 
Bunsen flame, or a spirit-lamp. What collects on the sides of 
the tube, what escapes, and what remains behind? Burn this 
remainder on platinum foil, and what will then remain? 

Queries. What did you obtain from the wood 1 What became of the 
charcoal when burned ? Did any tar escape with the smoke ? How do 
you know? Any water % Prove it. (Sijg. Hold a piece of cold glass 
in the escaping vapors.) Will a piece of brick give the same results ? 
Try it. 

Exp. 3 p. Place in a hard glass tube, open at both ends, a 
small piece of galena (PbS). Hold the tube somewhat slant- 
ing in the Bunsen flame, so that the greatest heat shall strike 
underneath the galena. Notice the odor of the fumes which 
soon issue from the tube. These are the fumes of burning sul- 
phur. Now place the residue in a shallow, cup-shaped cavity, 
which you are to make in a piece of charcoal. Cover the resi- 
due with sodium carbonate (Na 2 C0 3 ) , and slightly moisten the 
whole. Heat it before the blow-pipe flame and you will obtain 
a metallic bead. What metal is it ? 

It is evident that wood and galena are not elements ; 
and, as the student's experience increases, he will learn 
that there is a very large class of substances which can 
thus be separated into simpler ones, and that these simpler 
substances are united in definite proportions by weight. 
Hence the following name and definition : — 

9. A Compound (chemical) consists of two or more ele- 
ments chemically combined in definite proportions. 
(Art. 17.) 

Ex. Salt (NaCl) ; Water (H 2 0) ; Sugar (C 12 H 22 O u ). 



INTRODUCTION. 11 

Exp. 4 p. Mix thoroughly 0.56 s of very fine iron-filings 
and 0.32 g powdered sulphur. Although the mixture resembles 
neither iron nor sulphur, this is only a mechanical mixture, 
and the microscope reveals the particles of iron and sulphur 
lying side by side : moreover, they may be separated by 
mechanical means. Now heat one-half the mixture to red- 
ness in an iron spoon ; a glow diffuses itself throughout the 
mass, and the iron combines with the sulphur in definite pro- 
portions. No microscope can now distinguish the iron and 
sulphur particles, nor can they be separated except by chemi- 
cal means. The iron and sulphur have exactly entered into 
chemical union. 

Queries. Can you, with a magnet, separate the iron from the sulphur 
before heating? Try it. Will bisulphide of carbon (CS 2 ) dissolve out the 
sulphur from the iron particles before heating 2 Try it. Should the sul- 
phur dissolve, evaporate the solution to dryness on a watch crystal, and 
see if the sulphur will remain as a residue. 

After heating, pulverize the mass and try as above. What difference 
do you find 2 

From the above we derive the two following defini- 
tions : — 

10. A Mechanical Mixture is formed when substances 
are put together in no definite proportions, and the result- 
ing substance retains the properties of its constituents. 

11. A Chemical Combination or Reaction takes place 
when two or more substances unite in definite proportions 
to form one or more substances entirely different from 
the original ones. 

12. Chemistry is that science which treats of the ele- 
ments found in nature, their properties, compounds, and 
actions and reactions upon one another. 

Matter exists in three forms ; viz., Solids, Liquids, and 
Gases. 



12 INTRODUCTION. 

13. Solids do not readily change their forms, since in 
them the attractive (inter-molecular) forces exceed the 
repellent forces. 

14. Liquids do readily change their forms, since their 
attractive and repellent (inter-molecular) forces are equal, 
or nearly so. 

15. In G-ases, the repellent forces are greater than the 
attractive forces, consequently gases always tend to occupy 
a larger space. 

Sug. Name several solids. Liquids. Gases. Show, by heating a 
piece of ice till it vaporizes, that water exists in all three conditions. 

16. Chemism is an attractive force which is exerted 
between the elements, causing them to enter into com- 
bination with one another. 

Note. Cohesion and- chemism tend to draw particles together. In all 
solid and liquid compound bodies, both chemism and cohesion operate : 
the former holds the elements together, and determines the composition 
of the body ; the latter holds the particles of the compound together, and 
gives us the mass. Heat is a repellent force, and tends to separate the 
small particles of all bodies, as is shown by the expansion of bodies when 
heated. 

17. Law of ^Definite Proportions. — If we examine 
any chemical compound, — such, for example, as water, 
which consists of the elements hydrogen and oxygen ; 
common salt, which consists of the elements sodium and 
chlorine, — we find that the compound always contains 
exactly the same proportions of its constituents. Water 
always contains 88.89 per cent of oxygen and ll.li per 
cent of hydrogen ; common salt always contains 39.32 per 
cent of sodium and 60.68 per cent of chlorine. As a re- 
sult of the careful analysis of a very large number of 



INTRODUCTION. 13 

chemical compounds, the law of definite proportions was 
propounded. The law may be stated in this form ; — 

Any given chemical compound alivays contains the same 
elements in the same proportions by iveight. 

Rem. It is, of course, impossible for the beginner to prove the cor- 
rectness of this law, for the reason that the proof cannot be furnisher] 
without the employment of some of the most delicate and difficult chemi- 
cal processes. 

18. Law of Multiple Proportions. — Some elements 
form more than one compound with each other. Thus 
hydrogen and oxygen form not only water but hydrogen 
dioxide ; iron and sulphur form three compounds : nitro- 
gen and oxygen form five compounds. If Ave examine the 
proportions by weight in which the elements unite, we find 
very curious and interesting relations. Thus, in water we 
find : hydrogen 1 part, oxygen 8 parts ; in hydrogen diox- 
ide, hydrogen 1 part, oxygen 16 parts. (See Art. 38.) 

In the compounds of iron and sulphur (Art. 293), there 
are : 

Compound 1 , 32 parts of sulphur and 56 parts of iron. 
Compound 2, 64 " " ." 56 " " 

Compound 3, 96 " tc " 112 " " 

In the compounds of nitrogen and oxygen (Art. 56), 
there are: 

Compound 1, 28 parts of nitrogen and 16 parts of oxygen. 
Compound 2, 28 " ^ " 32 " " 

Compound 3, 28 " " " 48 " " 

Compound 4, 28 " " " 64 « " 

Compound 5, 28 iC " " 80 " " 

The amount of oxygen in the second compound of 
hydrogen and oxygen is just twice as great, — not one 



14 INTRODUCTION. 

and one-half, nor any fractional number of times, as great, 
as in the first. 

The amounts of sulphur in the three compounds of iron 
and sulphur bear to each other the relation of 1 : 2 : 3 ; and 
the amounts of iron are to each other as 1 : 1 : 2. 

Finally, in the compounds of oxj'gen and nitrogen, the 
amounts of oxygen are to each other as 1:2:3:4:5; the 
amount of nitrogen remaining constant. 

These cases illustrate what is known as the law of multi- 
ple proportions* which may be stated thus : 

If tivo elements* A and B* form several compounds with 
each other* and we consider any fixed amount of A* then the 
different amounts of B which combine with this fixed amount 
of A bear a simple ratio to each other, 

19. Combining* Number. — For each element we can 
select a certain number which will enable us always to 
express the proportion by weight in which this element 
enters into combination. 

Thus, we may select the number 16 for oxygen, and we 
find that no matter what the compound may be in which 
we find the oxygen, its proportion may be expressed by 16 
or some simple multiple of 16. In the same way we find 
that 32 may be selected for sulphur ; 14 for nitrogen ; 56 
for iron, etc., etc. The figures thus selected are known as 
the combining numbers. Elements always combine with 
each other in the proportions expressed by their combin- 
ing numbers, or by simple multiples of these numbers. 
Thus, according to this, if sulphur and oxygen unite, we 
would expect to find them in their compounds in the 
proportions of 32 parts of sulphur to 16 parts of oxy- 
gen ; 32 parts of sulphur to 32 parts of oxygen ; 32 parts 
of sulphur to 48 parts of oxygen, etc. Compounds cor- 



INTRODUCTION. 15 

responding to the last two proportions are known. (See 
Art. 164.) 

20. Atomic Theory. — To account for the fact that ele- 
ments unite in fixed proportions, it is assumed that all 
matter is made up of indivisible particles called atoms, and 
that each different kind of atom has its own particular 
weight. When chemical combination takes place, it is 
supposed that this consists of a union of the atoms of the 
elements which take part in the action. Thus, when iron 
and sulphur are brought together, at first no action takes 
place ; but when they are very intimately mixed, and the 
mixture heated, it is believed that each atom of iron seizes 
upon an atom of sulphur, uniting with it. Now, as these 
atoms have definite weights, it follows that, no matter how 
many unite, the compound formed must always contain 
the elements in the proportion of the weights of the atoms. 

The simplest kind of combination is that in which the 
elements unite in the proportion of one atom of one ele- 
ment to one of the other. But the elements may unite in 
the proportion of one atom of one to two, or three, or even 
four of the other, etc. Or, two atoms of one may unite 
with three of another, etc. Hence : it follows that the 
amounts of any element found in different compounds 
must bear simple relations to each other. 

21. Atomic Weights. — The numbers called combining 
numbers are believed to express the relative iveights of the 
atoms of the elements, and are now called atomic weights* 
The numbers now in use are intended to express the 
weights of the atoms of the elements as compared with the 
weight of the atom of hydrogen taken as unity. Thus, 
when we say that the atomic weight of oxygen is 16, and 
that of nitrogen 14, we mean that the weight of the atom 



16 INTRODUCTION. 

of oxygen is 16 times as great as that of the atom of 
lydrogen ; and that the weight of the atom of nitrogen is 
14 times as great as that of hydrogen. 

22 Determination of Atomic Weights. — To deter- 
mine the atomic weight of an element is by no means a 
simple matter; indeed, it is extremely difficult. If all 
the elements united with each other in only one propor- 
tion it would not be difficult to agree upon atomic weights. 
Thus chlorine and hydrogen unite with each other in the 
proportion of 35.5 parts of chlorine to 1 of hydrogen ; 
bromine and hydrogen in the proportion of 80 parts of 
bromine to 1 of hydrogen ; iodine and hydrogen in the 
proportion of 127 parts of iodine to 1 of hydrogen ; and 
these elements do not unite with hydrogen in any other 
proportions. Hence, we may assume that in the com- 
pounds formed we have, in the first place, one atom of 
chlorine united with one atom of hydrogen ; in the second, 
one . atom of bromine with one of hydrogen ; and in the 
third, one of iodine with one of hydrogen. We are thus 
led to the conclusion that the atom of chlorine weighs 
35.5 times as much as the atom of hydrogen, or that the 
atomic weight of chlorine is 35.5 ; and, in the same way, 
that the atomic weight of bromine is 80, and that of iodine 
127. 

When, however, two elements unite in more than one 
proportion, — and this is the rule rather than the excep- 
tion, — it is cleir that we must be left in doubt as to the 
number to select as the atomic weight. Thus, hydrogen and 
oxygen, as was remarked above, unite in two different pro- 
portions. In the first there are 8 parts of oxygen to 1 of 
hydrogen ; in the second, 16 parts of oxygen to 1 of hydro- 
gen. From this we might conclude that 8 is the atomic 



INTRODUCTION. 17 

weight of oxygen. But Ave may just as well express the 
proportions by saying that in the first there are 16 parts 
of oxygen to 2 of hydrogen ; and in the second, 16 parts 
of oxygen to 1 of hydrogen. And we might, with equal 
justice, conclude that 16 is the atomic weight of oxygen. 

We shall find that two methods are in general use for 
the determination of atomic weights. The first is based 
upon a consideration of the specific gravity of elements 
and compounds in the form of gas or vapor ; the second, 
upon the specific heat of elements and compounds. These 
methods will be described after some of the elements and 
their compounds have been considered. (Art. 157.) 

23. Names of the Elements. — The ancients were 
acquainted with only seven elements ; viz., gold, silver, 
copper, iron, mercury, lead, and tin. They dedicated 
these to the heavenly bodies ; e.g., silver was dedicated 
to the moon or luna. In this fanciful way some of the 
names of chemical compounds originated ; e.g., nitrate of 
silver is yet called lunar caustic. 

The elements have received their names in different 
ways : — 

1. Some retain their ancient names. 

2. Some are named from some marked characteristic; 
e.g., phosphorus, light-hearer ; bromine, a stench. 

3. The names of some end in "ine" or "on," to indi- 
cate a similarity of properties in those so terminating. 

4. Some are named from the place of their discovery. 

5. The names of recently discovered substances pos- 
sessing metallic properties end in "urn" or "ium." 

Sug. Student find illustrations to above from Art. 25. 

24. Symbols. — In expressing the composition of chemi- 
cal compounds, it is desirable to have a system of symbols. 



18 INTRODUCTION. 

Those now in use consist of letters which stand for the 
names of the different elements. Thus, O stands for Oxy- 
gen, H for Hydrogen, N for Nitrogen, etc. 

When only one element is known, whose name begins 
with a certain letter of the alphabet, that letter is used 
as the symbol. 

When two or more are known, the names of which begin 
with the same letter, that one best known or first discov- 
ered is generally designated by the letter, while the others 
are designated by this letter and some other letter occur- 
ring in the name, e.g., Carbon, C ; Chlorine, CI ; Calcium, 
Ca; Caesium, Cs ; Cadmium, Cd; Cobalt, Co; etc. 

Some elements have symbols derived from their Latin 
names. This is perplexing to the student, but this list 
will explain : — 

Antimony, Sb, from Stibium. 

Copper, Cu, " Cuprum. 

Gold, Au, " Aurum. 

Iron, Fe, " Ferrum. 

Lead, Pb, " Plumbum. 

Mercury, Hg, " Hydrargyrum. 



Potassium, K, from Kalium. 
Silver, Ag, " Argentum. 

Sodium, Na, " Natrium. 
Tin, Sn, " Stannum. 

Tungsten, W, " Wolframium. 



The symbol stands not only for the name of the element, 
but for its atom. Thus, O means not only oxygen, but an 
atom of oxygen ; 2 O or 2 means two atoms of oxygen, 
etc. In expressing the composition of bodies by means of 
these symbols, we simply place the latter side by side. 
Thus, HC1 stands for a body which consists of hydrogen 
and chlorine in the proportions, 1 part by weight of hydro- 
gen to 35.5 of chlorine ; or, in terms of the Atomic Theory, 
it stands for a body which is formed by the union of hydro- 
gen and chlorine in the proportion of 1 atom of hydrogen 
to 1 of chlorine. An expression like HC1 is called a for- 
mula. 



INTRODUCTION. 19 

In expressing the composition of a body in which more 
than one atom of the same kind is present, a small figure 
is added below the line to the right of its symbol. Thus, 
potassium nitrate, which consists of potassium, nitrogen, 
and oxygen, in the proportion of 1 atom potassium, 1 
nitrogen, and 3 oxygen, is written KN0 3 . A large figure 
placed before a formula affects every symbol in the for- 
mula. Thus, if we want to express two parts of potassium 
nitrate, we usually write 2 KN0 3 , and not (KN0 3 ) 2 . We 
repeat a group of atoms (N0 3 , NH 4 , etc.) which we wish 
to keep together as a whole (Art. 159), thus : Pb(N0 3 ) 2 , 
(NH 4 ) 2 S. 

Following is a list of the elements which have thus far 
been discovered. The table includes not only the names 
of the elements, but their atomic symbols, atomic weights, 
— as determined by every available method, — and their 
specific gravities. 

The small Roman numerals or indices added to the sym- 
bols are intended to indicate the valence (see Art. 158) 
of the elements. Usually the symbol is written without 
these. 

The following rare elements have recently been listed: — 



Argon, 


A, 


39.9 


Xeon, 


Ne, 


20. 


Gadolinium, 


Gel, 


156. 


Radium, 


Ra, 


225. 


Germanium, 


Ge, 


72.5 


Thulium, 


Tm, 


171. 


Helium, 


He, 


4. 


Xenon, 


x, 


128. 


Krypton, 


Kr, 


81.8 









20 



INTRODUCTION, 



25. A Table of the Elements. 









Physical 




Names. 


Symbols. 


Atomic 
Weights. 


condition at 

ordinary 
temperature. 


Specific Gravity. 


Aluminum 


Al"" 


27. 


Solid 


2.60 


Antimony 


Sb"'- V 


120.2 


t. i 


6.71 


Arsenic 


As'"- V 


75. 


l< 


5.73 


Barium 


Ba" 


137.4 


U 


3.75 


Beryllium * 


Be" 


9. 


cc 


2.07 


Bismuth 


Bi'"' v 


208.5 


u 


9.80 


Boron 


B "' 


11. 


a 


2.5? 


Bromine 


Br '.' 


80. 


Liquid 


3.187 


Cadmium 


Cd" 


112.4 


Solid 


8.60 


Caesium 


■ Cs' 


133. 


ci 


1.88 


Calcium 


Ca" 


40.1 


cc 


1.57 


Carbon 


C"" 


12. 


cc 


3.5-.6 


Cerium 


Ce'"'"" 


140. 


cc 


Q.68 


Chlorine 


Cl'- T 


35.5 


Gas 


2.450 


Chromium 


Cr""- Ti 


52.1 


Solid 


6.50 


Cobalt 


Co"-"" 


59. 


u 


8.5-.7 


Copper 


Cu" 


63.6 


cc 


. 8.95 


Didymium 


D'" 


Pr, 140.5: Xd, 
143.5 


u 


6.54 


Erbium 


E'" 


166. 


-4; 


— 


Fluorine 


F' 


19. 


Gas 


1.313 


Gallium 


G"" 


70. 


Solid 


5.95 


Gold 


An'-'" 


197.2 


CC 


19.32 


Hydrogen 


H' 


1. 


Gas 


0.069 


Indium 


In"" 


114. 


Solid 


7.42 


Iodine 


I',v 


127. 


cc 


4.948 


Iridium 


JyJI,llll,Vi 


193. 


cc 


22.42 


Iron 


jp e tt, Ml, Yi 


56. 


cc 


7.86 


Lanthanum 


La'" 


138.9 


cc 


6.10 


Lead 


Pb"> "" 


207. 


cc 


11.37 


Lithium 


Li' 


7. 


6 c 


0.59 


Magnesium 


JVJo-/', HI, vi 


24.3 


cc 


1.74 


Manganese 


Mn" 


55. 


i c 


8.03 


Mercury 


Hg" 


200. 


Liquid 


13.55 


Molybdenum 


Mo"-""- vi 


96. 


Solid 


8.60 


Nickel 


Ni", "" 


58.7 


cc 


8.90 



* Or Glucinum, Gl. 



INTRODUCTION. 



21 









Physical 




Names. 


Symbols. 


Atomic 
Weights. 


condition at 

ordinary 
temperature. 


Specific Gravity. 


Niobium * 


Nb v 


94. 


Solid 


7.06 


Nitrogen 


N"',v 


14. 


Gas 


0.971 


Osmium 


0s »."".vi 


190.8 


Solid 


22.48 


Oxygen 


0" 


16. 


Gas 


1.105 


Palladium 


Pd"' nn 


106.5 


Solid 


11.40 


Fhosphorus 


p', '", v 


31. 


- { 


Colorless 1.83 
Red 2.20 


Platinum 


Pt">"" 


195. 


44 


21.50 


Potassium 


K' 


39.2 


i i. 


0.87 


Rhodium 


Ro /;,f^,vi 


103. 


44 


12.10 


Rubidium 


Rb' 


85.5 


44 


1.52 


Ruthenium 


Ru f/,/m,yi 


101.7 


£1 


12.26 


Samarium 


Sm 


150. 


44 


— 


Scandium 


. Sc 


44. 


44 


— 


Selenium 


Se"'""'* 


79. 


44 


4.50 


Silicon 


Si"" 


28.4 


. 44 


2.39 


Silver 


Ag' 


108. 


44 


10.53 


Sodium 


Na' 


23. 


k< 


0.978 


Strontium 


Sr" 


87.6 


4 4 


2.54 


Sulphur 


yr, mi, xi 


32. 


44 


2.05 


Tantalum 


Ta v 


183. 


44 


10.40 


Tellurium 


r Pe"' ""> vi 


127.6 


44 


6.40 


Terbium 


Tb 


160. 


u 


— 


Thallium 


Tl''' 7 ' 


204. 


44 


11.85 


Thorium 


Th ,w 


232.5 


44 


11.00 


Tin 


Sn n,im 


119. 


44 


7.29 


Titanium 


^[HJUf 


48. 


It 


— 


Tungsten 


WU!,vi 


184. 


44 


19.12 


Uranium 


Tj7W,vi 


238.5 


44 


18.70 


Vanadium 


ym,v 


51.2 


u 


5.50 


Ytterbium 


Yb 


173. 


u 


— 


Yttrium 


Y'" 


89. 


4 4 


— 


Zinc 


Zn" 


65.4 


" 


7.15 


Zirconium 


Zr"" 


90.6 


44 


4.15 



* Or Columbium. Cb. 



22 INTRODUCTION. 

Rem. 1. Many elements occurring in the earth have also been dis- 
covered in the sun and stars. 1 

Rem. 2. Some elements occur in such very small quantities that their 
properties are not accurately known ; while others have been discovered 
so recently that they have not been fully investigated. (See Chem. News, 
Feb. 13, 1903, for List of Elements. 

Rem. 3. More elements will be discovered, undoubtedly; and some 
substances now known as elements may prove to be chemical compounds, 
as our chemical researches advance. Thus Didymium has been separated 
into Neodymium and Prsesodymiuru. 

Rem. 4. In estimating the specific gravity of the elements, icater is 
taken as the standard for solids and liquids, while air is taken for gases. 

Rem. 5. The chemist also uses hydrogen as a standard for estimating 
the density of gases, as will be explained later. 



SUMMARY OF STUDENT'S WORK IN INTRODUCTION. 

1. Make those experiments whose numbers are followed by the letter 
"p." 

General Note. When "p" follows the number of an experiment, the 
student should be able to do the work : if, however, the student cannot 
do the work, owing to various causes for which no text can provide, or if 
the teacher wishes the work done differently, a few simple oral directions 
from the teacher to the class will assist greatly. 

Experiments marked " t " are to be made by the teacher before the 
class. Let the pupils assist as much as possible. 

In experiments marked "tp," it is advisable for the teacher to make the 
experiment for the class before requiring the student to do it. 

Experiments marked " op" are optional. 

Encourage the student to exert his ingenuity in overcoming obstacles 
and he will soon become quite independent in manipulation. 

1 The element Helium was first discovered in the sun's chromosphere c 
Ramsay has discovered the same gas in uranite, or cleveite, an impure 
uranate of lead. 

Helium also occurs in certain springs in the Pyrenees and in the Black 
Forest. 

Helium has an atomic weight of about He = 4. 



CHAPTER I. 

OXYGEN : ITS OCCURRENCE, PREPARATION, PROPERTIES , 
AND TESTS. OZONE. 

THE ELEMENT OXYGEN. 

Symbol O". — Atomic Weight, 16; Specific 
Gravity, 1.1056. 

26. Occurrence. — Oxygen occurs well-nigh everywhere 
in nature. It constitutes 44 to 48 per cent of the weight 
of the earth's crust, 88.89 per cent of water, and about 
23 per cent of the atmosphere. 

Oxygen occurs in combination with every known ele- 
ment except fluorine. 

27. Preparation. — Exp. 5 p. Heat one gram mercuric 
oxide, HgO, in a hard glass test-tube. The oxygen is driven 
off, while the mercury is condensed on the sides of the tubec 
Test the presence of the gas with a glowing match. (HgO = 
Hg + O.) 

Query. Aug. 1, 1774, Joseph Priestley made this experiment for the 
first time. What gas did he discover 1 

Exp.. 6 p. Minium, or red oxide of lead. Pb 3 4 , is to be 
heated as above. A part of the oxygen is driven from the 
red oxide of lead with great difficulty. (Pb 3 4 = 3 PbO + 0.) 
Test as before. 

Sug. Try KC10 3 with and without Mn0 2 , as above. Also heat, as 
above, KC10 3 with a pine splinter. What occurs 1 Explain. 



24 THE ELEMENT OXYGEN. 

Queries. Why does not the red oxide of lead, Pb 3 4 , part with its 
oxygen as readily as mercuric oxide, HgO 1 Ans. The lead has a stronger 
chemism for oxygen than mercury has. It is upon the principle of variable 
degrees of chemism existing between different substances, that double 
chemical reactions are always based. Do you obtain metallic lead in this 
experiment ? Heat some red oxide of lead on charcoal, with sodium car- 
bonate (Na 2 C0 3 ), before the blow-pipe. Do you now obtain metallic lead ? 
What effect do the sodium carbonate and charcoal have on substances 
treated thus ? Ans. The charcoal abstracts oxygen from the oxide, or 
acts as a strong reducing agent. The sodium carbonate serves as a " flux/' 
preventing the lead from again taking up atmospheric oxygen. 

Oxygen can be prepared most easily from the com- 
pounds which it forms with other elements; as, mercuric 
oxide, HgO ; manganese dioxide, Mn0 2 , potassium chlo- 
rate, KCIO3, etc. 

Potassium chlorate, KC10 3 , is the most available sub- 
stance for preparing moderately large quantities in small 
laboratories ; but if very large quantities are required, it 
may be prepared more cheaply from manganese dioxide, 
although special apparatus is necessary. 

Potassium chlorate gives up its oxygen more readily 
and at a lower temperature when mixed with manganese 
dioxide (KC10 3 = KC1 + 30). The manganese dioxide is 
unchanged. This method is best for laboratory use. 

Exp. 7t. Pulverize 100 g potassium chlorate, KC10 3 , and mix 
thoroughly with 25 g manganese dioxide, Mn0 2 . Place the mix- 
ture in an iron or copper retort, and arrange to wash the gas 
through two Wouiff bottles : the first containing water, the sec- 
ond sodium hydroxide, NaOH. Now heat strongly but care- 
fully, and, when the air is expelled from the apparatus (test 
with a match) , connect with the gas receiver. Notice that at 
a certain point the gas is given off with great rapidity. The 
heat must be moderated immediately to avoid accident. Yon 
will thus obtain about 30 1 of pure oxygen gas. 



THE ELEMENT OXYGEN. 25 

Caution. Organic matter or carbon, when present, may produce a 
serious explosion. It is best, therefore, to try a little of this mixture in a 
test-tube before heating the retort. Use C. P. materials. 

Note. It is always best to have the class present when preparing 
such experiments as this last. Arrange the pneumatic trough, bell jars 
wires, etc., and make the following experiments in a dark room. 

28. Properties of Oxygen. — Exp. 8 t. Plunge into a jar 
of oxygen a glowing pencil of thoroughly charred bark charcoal. 
It will burn with brilliant scintillations. (C +2 0= C0 2 -) 

Note. This illustrates the combustion of fuel. 

Exp. 9 t. Place a bundle of very fine iron wires, tipped 
with sulphur and ignited, in a jar of oxygen. The wires will 
burn with a reddish light, and at times with beautiful scintilla- 
tions. (3 Fe + 4 O = Fe 3 4 .) 

Note. This illustrates the great chemical activity of pure oxygen- 

Exp. 10 t. File the end of a watch-spring till very thin. 
Draw the temper in a spirit-lamp, and uncoil it. Make a 
hook on the thin end, tip with sulphur, and ignite. Place 
in a jar of oxygen. The spring will burn with great energy. 
(3Fe+40 = Fe 3 4 .) * 

Exp. 11 t. Place a piece of phosphorus in a jar of oxygen. 
Ignite. It burns with a brilliant white light. (2 P + 5 O = P 2 5 . ) 
See Phosphorus. 

Exp. 12 t. Treat a piece of sulphur as in last experiment. 
It burns with a violet light. (S + 2 O = S0 2 .) 

Note. Do not allow the fumes from the burning of phosphorus and 
sulphur to escape in the room, as they are very disagreeable. 

Exp. 13 t. Cut zinc foil into fine strips ; make into a bundle ; 
tip with sulphur ; ignite. White light in oxygen. (Zn + O — 
ZnO.) 

Note. The product formed is called " Philosopher's Wool." 



26 THE ELEMENT OXYGEN. 

Now that you have prepared and experimented with 
oxygen, you will be ready to appreciate several of its 
physical and chemical peculiarities which we term prop- 
erties. Oxygen is an invisible, odorless, tasteless gas. Its 
specific gravity is 1.10563 ; and l 1 at 0° and 760 mrn pressure 
weighs 1.480 g . 

It has been liquefied by a pressure of 25.85 atmospheres 
at a temperature of —131.6°. (Read R. and S., pp. 74- 
84, Vol. I., Rev. Ed.) 

Exp. 14 op. Place a live mouse upon a cork raft, under a 
bell jar filled with air, over the pneumatic trough. Secure the 
jar so that no communication with the outside air is possible. 
Does the water rise in the jar? What does this indicate? 

Queries. How does the oxygen come in contact with the blood ? 
What harm ensues from persons living in a room without ventilation ? 
Is the blood purified by a physical or chemical process 7 

Oxygen is that constituent of air which is essential to 
breathing, and all animals consume it. When inhaled, it 
enters into combination with some of the tissues of the 
body, actually burning them out, and thus liberating heat 
and energy. Air that has been breathed over too many 
times loses its vitality, the oxygen having been consumed. 

As oxygen occurs in the atmosphere, it is largely diluted 
with nitrogen. 

Exp. 15 op. Place a live fish in a sealed jar of water. What 
follows ? Why ? 

Water absorbs free oxygen, and fishes consume this 
oxygen by means of their gills, which serve as lungs. 

Query. How does a jet fountain render water fit for preserving the 
life of fishes ? 



THE ELEMENT OXYGEN. 



27 



Exp. 16 of. Place a burning taper in a closed jar of air. 
When the oxygen of the air is consumed, what occurs? 

Queries. Why does blowing the fire cause it to burn more briskly 1 
Why does blowing a candle extinguish it 2 (See next Exp.) 

Fire or Combustion is produced by the union of the 
fuel with atmospheric oxygen. Before a substance can 
unite with oxygen, it must be heated to what is called its 
burning temperature or kindling point ; and to produce 
flame, it must be converted into a gas. A flame is a burn- 
ing gas. 

Exp. 17 p. Carefulhy place a bent glass tube very near the 
wick of a lighted candle, within the flame zone. The gas 
escaping from the wick will be forced up through the tube, and 
may be lighted at the other end of the tube. 

Since the gas which escapes from the wick burns only 
when mixed with air, the flame of a candle has but a 
thin outer zone, in which the gas is entirely consumed, 
(Fig. 1.) 

Explanation of Fig. 1. 

t, bent glass tube. 

c, centre of unconsumed gas. 

p, zone of incomplete combus- 
tion. 

f, light zone, or zone of com- 
plete combustion. 

f ; , unconsumed gas burning at 
end of glass tube. 

Queries. What does this ex- 
periment prove % Why can you 
not ignite a fump of anthracite 
coal with a match ? Why does 
a blow-pipe give such a hot 
flame ? Fig. 1. 





28 THE ELEMENT OXYGEN. 

Bunsen Burner. — This burner is almost exclusively 
used in laboratories provided with gas for heating purposes. 
It gives a very hot, clean flame, owing to the fact that it 
is so arranged that the gas, before ignition, is thoroughly 
mixed with air, which insures its complete combustion^ 
The tube e, shown in Fig. 2, is pierced with holes at its 
base, and the gas is discharged at about the 
height of these holes. Now, as the gas ascends 
the tube e, it draws a current of air along with 
it ; the air and gas mix in their ascent through 
e, and burn with a hot, non-luminous flame 
when ignited at the top of e. A ring a pierced 
with holes surrounds e ; by turning this ring, 
the holes del maybe closed, when the gas burns 
with an ordinary luminous flame, which is the 
flame used for the blow-pipe. And here the 
student may learn the meaning of the terms Oxidizing 
Flame and Reducing Flame, for which he will hereafter 
find frequent application. The way in which these flames 
are produced is as follows : — 

1. The Oxidizing Flame. — First close the openings^, 
and make a moderately small luminous flame. Now place 
the tip of the blow-pipe in the centre of the luminous 
flame, and blow gently, using the cheeks like a bellows. 
The oxidizing flame should be non-luminous. In case 
you do not succeed in making it so, do not try to remedy 
the evil by blowing harder, which will end only in ex- 
hausting you, but moderate the flow of gas, and try again. 
After a little practice you should be able to keep the flame 
steady for naif an hour, without becoming much fatigued. 
This flame teuds to oxidize substances when they are 
placed in it, since it contains an excess of oxygen at a 
very high temperature. 



THE BLEMENl OXYGEN. 29 

Queries. Whence comes this excess ? Should air from the lungs be 
used in blow-piping ! Why ? 

' Sug. Examine a blow-pipe, and give a short description. 

2. The Reducing Flame is made by placing the jet of 
the blow-pipe just outside of the luminous flame from the 
burner, with the openings closed. This flame is slightly 
luminous, and reduces or takes oxygen away from bodies 
placed in it, since it contains an excess of hydrogen and 
carbon (illuminating gas is a hydrogen-carbon compound) 
at a high temperature ; both hydrogen and carbon have a 
strong affinity for oxygen. 

Moreover, the bead, or assay, is to be kept within the 
zone of complete combustion (Fig. 1) when you are using 
the oxidizing flame ; when using the reducing flame, the 
proper position of the assay is within the zone of incom- 
plete combustion. 

Query. If you use your lungs for bellows, can you keep the blow-pipe 
flames steady 2 

Exp. 18 p. Make a borax bead by fusing borax on a loop of 
platinum wire. Slightly moisten this bead in ferrous sulphate, 
FeS0 4 , and heat a short time in the oxidizing flame. The bead 
thus treated should be of a reddish color when hot, fading to a 
light yellow when cold. Now heat the same bead persistently 
in the reducing flame. It should become colorless unless too 
strongly saturated with the ferrous sulphate, when it becomes 
pale green. Unless the proper flames are used, these results 
cannot be obtained. 

Spontaneous Combustion. — The combination of oxygen 
and other substances always produces a definite amount of 
heat depending upon the nature of the substance. When 
iron rusts slowly, the heat is imperceptible ; but when 
greasy rags or waste are thrown in a heap, the heat pro- 



30 THE ELEMENT OXYGEN. 

duced by the oxidation of the oils may, in time, be suffi 
cient to raise the mass to the temperature of ignition. 
This kind of action, known as spontaneous combustion, is 
not unfrequently the cause of disastrous fires. 

Exp. 19 p. Sift very fiue iron-filings over the flame of an 
ordinary lamp. What results? 

Query. Why is this ? What does it illustrate ? 

Sug. Try fine dust from a malt house, flour mill, wood-working shop, 
etc., as above. The best place to collect the dust is from rafters or high 
beams. Why 1 

Fine dust collecting in the attics of large mills and malt 
houses has sometimes exploded when ignited, causing great 
destruction of life and property. Again, the sun's rays, 
when brought to a focus on inflammable substances, or 
steam pipes coming in too close proximity to inflammable 
substances, have produced unlooked-for conflagrations. 

Exp. 20 p. Place green plant-leaves in the sunlight, under 
a bell jar filled with water. Bubbles of oxygen will collect at 
the top of the jar. 

Oxygen is given off by plants growing in the sunlight. 
Enough oxygen is returned to the air in this way to keep 
its composition nearly uniform. 

29. Tests for Free Oxygen. - - 1. Char a small pine 
stick, as a match, and, with one end glowing, place it in 
a jar or current of free oxygen, when it will burst into 
flame. 

2. Fill a flask with oxygen gas. Pour in a small quan- 
tity of potassium hydroxide, KOH. Shake, and no change 
in the liquid takes place. Then add a small quantity of 
pyrogallic acid, C 6 H 3 (OH) 3 . Shake again, and the liquid 
turns brown, oxygen being absorbed. 



OZONE. 31 

N.B. In testing an unknown gas in this way, it is absolutely necessary 
to exclude all air, as the free oxygen of the air gives this reaction. It is 
best, therefore, to fill the flask over mercury. (See App.) 



OZONE. 

30. Ozone is a peculiar or allotropic form of oxygen 
found in the atmosphere, and produced by electrical dis- 
charges, or by evaporation, or by both. When an element 
occurs in more than one form, the unusual one is called 
an allotropic form. It is easily prepared by several 
methods. 

31. Preparation. — Exp. 21 p. Place a small quantity of 
a solution of potassium permanganate, KMn0 4 , in a flask or 
test-tube. Add a few drops strong sulphuric acid, H 2 S0 4 . 
Notice the odor of the gas given off. It is ozone. Apply 
Test 1 for ozone. 

Ozone may be prepared by suspending a clean stick of 
phosphorus in a closed jar containing a little water and 
atmospheric air at a temperature of 15° to 20°. Ozone is 
formed very rapidly. 

When an electrical machine, in good working order, is 
in action, a peculiar odor is observed which is due to 
ozone. (Use Test 1, Art. 33, for ozone.) 

Ozone may also be obtained by passing a silent electri- 
cal discharge, carefully avoiding sparks, through a closed 
jar of oxygen. 

Sug. Produce ozone by one or all of the above methods. 

32. Properties. — Ozone is three volumes of oxygen 
condensed to two volumes, the condensation being proba- 
bly accompanied by some deep-seated change in the relation 
of the atoms. 



32 OZOHE. 

There are good reasons for believing that the molecule 
(Art. 155) of ordinary oxygen consists of two atoms, as 
indicated by the formula 2 , and that the molecule of 
ozone should be represented by the formula 3 . Ozone 
is readily changed into ordinary oxygen. It is an active 
oxidizing agent. When brought in contact with mercury 
and some other substances in the dry state and at ordi- 
nary temperatures, it converts them into oxides, and itself 
becomes ordinary oxygen. 

Ozone readily acts upon organic substances, and is sup 
posed to destroy the germs of contagious diseases. When 
present in large quantities, ozone has an irritating effect 
on the lining membranes of the throat and nostrils, where- 
fore it should be dilute if inhaled. 

Atmospheric ozone is more plentiful in the open country 
than in cities, and more is found out of doors than in 
dwellings. (Why ?) 

Note. It is extremely difficult to determine whether the substance in 
the atmosphere which is commonly called ozone, is really ozone or not. 
There are certainly other substances present which in some of their 
properties closely resemble it; such, for example, as hydrogen dioxide 
(Art. 44). 

33. Tests for Ozone. — 1. A paper strip saturated with 
a solution of starch paste and potassium iodide, KI, turns 
blue when exposed to the action of ozone. 

Rem. This test is the one employed to determine the presence and 
amount of ozone in the atmosphere ; but it is not reliable, since some of 
the oxides of nitrogen, which also exist in the atmosphere, affect the paper 
similarly. 

2. Its odor, resembling dilute chlorine, betrays ozone 
when present in considerable quantities. 

3. Metallic mercury, Hg, when dropped into a flask 
containing ozone, immediately tarnishes. 



ozone* 33 



SUMMARY OF STUDENT'S WORK IN O. AND OZONE. 

1. Make the experiments as indicated. 

2. Make Tests 1 and 2, Art. 29 ; also test a flask of common air by 2. 
S. Make Tests 1, 2, and 3, Art. 33 ; also fit a delivery tube to the 

Florence flask used in Exp. 21 f 5 and direct the jet of ozone against a 
globule of Kg in the bottom of a test-tube. What result 1 

4. Allow the jet of ozone to pass into a test-tube containing a solution 
of starch paste and KL What occurs ? 

5. Read R. and S., Vol. L, p. 194, et seq., for a more complete discus- 
sion of ozone. 

6 Head Huxley's Elementary Lessons in Physiology on the arterialization 
of the blood. 

7. The manganese bead (Art 318) will furnish the student excellent 
practice in the use of the oxidizing and reducing flames. 

8. Will ozone give the oxygen test with the glowing match ? How 
can you distinguish between ozone and oxygen ? 

Argon. — In 1895 Rayleigh and Ramsay announced a 
new element discovered in the atmosphere, of which it 
constitutes nearly one per cent. It is a gas less active 
chemically than nitrogen. 

The gas is obtained from the atmosphere by a somewhat 
complicated process, the essentials of which consist in 
passing air first over red-hot copper to remove the oxygen 
and then over red-hot magnesium to remove the nitrogen. 

Argon has a density of about 20 ; and since its mole- 
cule is thought to be mon atomic, its atomic weight is 
about A = 40 (Ramsay). 

Olszewski has condensed argon to a liquid at —121° C. 
and 50.6 atmospheric pressure. 

Crookes has examined the spectrum of argon, which 
exhibits characteristic lines. 

Krypton, Neon, and Xenon also occur in the air in small 
quantities. They are obtained by the fractional evapora- 
tion of liquid air. 



CHAPTER II. 



HYDROGEN. 



-ITS OCCURRENCE, ETC. 
HYDROGEN DIOXIDE. 



WATER. 



HYDROGEN. 

Symbol H'. — Atomic Weight, 1; Specific Gravity, 0.0692. 

34. Occurrence. — Hydrogen is found, nearly always, 
combined with other substances. It occurs free, however, 
in very small quantities in certain volcanic gases, and 
absorbed in meteorites. 

It occurs combined with oxygen in the form of water, 
of which it constitutes 11.11 per cent by 
weight. 

It is a constituent of ammonia, coal gas, 
marsh gas, and of nearly all organic sub- 
stances. 

35. Preparation. — Exp. 22 t. Use the 

apparatus shown in Fig. 3. Add 1 part by 
weight of pure sulphuric acid, H 2 S0 4 , to 20 
parts distilled water ; then open the stop-cocks 
S and S f . Pour the acidulated water into the 
tube B until it issues from the tubes O and H. 
Then close the stop-cocks, and fill B up to the 
bulb. Connect the platinum wire Z, which is 
melted through the tube H, and terminates in 
a platinum strip, with the zinc pole of a Grove's 
battery consisting of five or six cells. Also 




HYDROGEN. 



35 



connect the platinum wire F (which is like Z in every respect) 
to the platinum pole of the battery. Hydrogen collects in tube 
H. and oxygen in tube 0. The hydrogen in tube H may be 
tested by slightly opening the stop-cock S f , and igniting. 
Hydrogen burns with a very hot flame, although it emits but 
little light. 




Queries. In which tube is the volume of gas greater ? How test the 
oxygen ? 

Exp. 23 t. Make an amalgam by rubbing, in a porcelain 
mortar, one-half gram metallic sodium, or potassium, together 
with 5 g mercury. 

Fill a jar with water, and 
arrange as in Fig. 4. Place 
the amalgam in a wire gauze 
cage, and insert under the 
mouth of the jar. The hy- 
drogen liberated rises and 
fills the jar. 

Test by carefully raising 
the jar, mouth downwards, 
and plunging a lighted taper 

upward into the jar. The taper is extinguished, but the 
hydrogen burns at the mouth of the jar. The taper may be 
relighted in this flame. Usually a harmless explosion ensues. 

Queries. What becomes of the mercury of the amalgam after being 
dipped into the water ? Drop apiece, not larger than a pea, of metallic 
sodium or potassium into a dish of warm water. What results ? Do 
you now see the reason for amalgamating the K or Na ? What is the 
reason ? Is the water alkaline ? (Alkalies turn a strip of red litmus 
paper, blue. Acids turn blue litmus paper, red.) 

Water may also be decomposed by passing steam through a heated 
tube containing finely divided iron or copper. The oxygen unites with 
the metal, while hydrogen is set free. (Write the equation ; see water- 
gas, p. 13G.) 



Fig. 4. 



36 HYDROGEN. 

Hydrogen is best prepared in a pure state by the de- 
composition of water. It maj r be prepared in many other 
ways ; but it then contains impurities from which it is 
difficult to free it. 

The action of potassium on water is expressed by the 
equation 

K + H 2 = KOH + H. 

Now let us inquire particularly as to the meaning of an 
equation. Primarily, it means that potassium and water 
give a substance called potassium hydroxide (KOH) and 
hydrogen. It will be seen that the sign -\- is read and, and 
the sign = is read give. But the equation means more 
than this. It tells us the exact proportions in which the 
substances act. For each one of the symbols stands foi 
a certain proportion of the element corresponding to its 
atomic weight. In the above, 39 parts of potassium act 
upon 18 parts of water (made up of 2 x 1 parts of hydro- 
gen and 16 parts of oxygen), and give the compound 
potassium hydroxide (made up of 39 parts of potassium, 
16 parts of oxygen, and 1 part of hydrogen), and 1 part 
of hydrogen. These relations are maintained whenever 
potassium acts upon water. From the use of a given 
amount of potassium, provided there be enough water, 
we get a definite amount of hydrogen. 

Problem. How much hydrogen will be formed if 100= of potassium 
were allowed to act upon water in such a way as to prevent the burning 
of the hydrogen ? How much potassium hydroxide will be formed ? 
How much water will be decomposed ? 

Sug. Teacher will give a number of other similar problems, calling 
attention to the fact that instead of saying parts we may say grams 5 
ounces, pounds, tons, or whatever unit of weight we may choose to take 
Student review the equations inclosed in parentheses, and explain. 



HYDROGEN. 



37 



Exp. 24 t. Place a quantity of granulated zinc in the gener- 
ating flask A, Fig. 5. Through the funnel tube B introduce a 
liberal quantity of dilute sulphuric acid, H 2 S0 4 , consisting of 
one part acid by weight to four of water. Allow the gas to 
escape through the delivery tube D for some time, to free the 
apparatus from air. Then collect in gas bags, or in the gas 
receiver, or in jars over the pneumatic trough. The reaction is 
represented by the equation 

Zn + H 2 S0 4 = ZnSO, + 2 H. 

We take no account of the water added, as it serves merely 
as a solvent for the zinc sulphate. ZnS0 4 . as fast as formed. 




Fig. 5. 



Hydrogen is prepared in large quantities, when absolute 
purity is not especially requisite, by allowing dilute acids 
(HC1, H 2 S0 4 ) to act on certain metals, such as iron and 
zinc. 

Xote. Hydrogen made in this way may contain sulphuretted hydro- 
gen and other impurities, which, for the most part, are destroyed- by pass- 
ing the gas through a solution of potassium permanganate. The gas may 
be dried by passing it through sulphuric acid or calcium chloride, or both. 
(Student should arrange an apparatus for making and purifying hydro- 
gen.) 

Having a quantity of hydrogen stored, teacher and 
students make the following experiments: — 



38 HYDROGEN. 

36. Properties. — Exp. 25 p. Fill collodion balloons to 
illustrate the lightness of hydrogen. Allow one or two of 
them to rise to the ceiling, and remain as long as they will. 
Even though they do not leak, they will, nevertheless, sink to 
the floor after a time. Why? 

Exp. 26 tp. Make hydrogen soap-bubbles, which will burn 
when touched with the flame of a taper. 

Queries. Are these bubbles heavier or lighter than air ? How can 
you tell the same of other gases ? 

Exp. 27 tp. Discharge the Lryclrogen pistol, illustrating the 
explosiveness of lrydrogen and oxygen. 

Query. Should you fill the pistol full of H, could you discharge it 1 
Why? 

Exp. 28 tp. Produce singing flame. To succeed well with 
this, lit a long, straight jet into a generating flask containing 
metallic zinc and dilute sulphuric acid. When the gas is coming 
off freely, light the jet. Hold glass tubes of various lengths and 
bores, down over the burning jet. In this way different tones 
may be produced. 

Query. What produces the tones ? 

Exp. 29 tp. Fill a bell jar with hydrogen, by holding the 
mouth of the jar downward, and allowing the hydrogen to flow 
up into the jar. Now reach up into the jar with an inverted 
dipper (ordinary) . Keeping the dipper bottom side up, draw it 
slowly downward out of the jar, and remove it some distance 
awa} r ; then bring a lighted taper under the dipper. What 
ensues ? Explain. 

Pure hydrogen is an odorless, tasteless, invisible gas, 
which was discovered and described by Cavendish in 1766. 

Its specific gravity (air = 1) is 0.0692. Hydrogen is 
the lightest substance known : l 1 at 0° C. and 760 1 
pressure, weighs 0.0896 g . 



mm 



HYDROGEN. 39 

Prob. How many grams H, at 0° and 760 mm , will a bell jar of 20 ; 
capacity hold ? 

Olszewski lias condensed hydrogen to a colorless, trans- 
parent liquid. He cooled the gas by surrounding it with 
liquid air boiling in a vacuum. The pressure first used 
was 180 atmospheres, which was afterward suddenly re- 
duced to 40 atmospheres. 

Hydrogen is highly combustible, burning with a very 
hot but slightly luminous flame, and, when mixed with 
considerable quantities of air or free oxygen, explodes 
with violence. 

The metal palladium absorbs hydrogen in large quan- 
tities at moderate temperatures. Platinum and iron also 
absorb it, but in much smaller proportion than palladium. 
It seems as if the hydrogen forms an alloy with them, 
acting very much like a metal itself. When a jet of 
hydrogen is directed against a piece of spongy platinum, 
at ordinary temperatures, so much heat is evolved as to 
cause the jet to ignite. Hydrogen is slightly soluble in 
water. It is not directly poisonous, but produces a weak 
ening and sharpening effect on the voice, when inhaled. 
It is very diffusible, and is apt to contain atmospheric 
air. The extreme lightness of hydrogen caused it to be 
used for filling balloons ; but, owing to its great diffu- 
sibility and the expense of its manufacture, it has been 
superseded by coal-gas. One gram of hydrogen, when 
burned, produces enough heat to raise the temperature 
of 34,462 s of water through one degree. Hence its ca- 
lorific power is said to be equal to 34,462 thermal units, 
— the thermal unit or Calorie being the amount of heat 
necessary to raise the temperature of one gram of water 
one degree Centigrade. 



40 



HYDROGEN AND OXYGEN COMPOUNDS. 



37 Test. — Hydrogen may be recognized by its flame, 
and behavior, as in the preceding experiments. 



HYDROGEN AND OXYGEN COMPOUNDS. 

38. Hydrogen and Oxygen form two chemical com- 
pounds ; viz. : — 

1. Water, H 2 ; and 

2. Hydrogen dioxide, H 2 2 . 

Water, H 2 0. 

39. Occurrence. — With water we are all well acquainted. 
It occurs everywhere, — -in streams, lakes, and the bound- 
less ocean. It exists in the 
atmosphere as vapors, fogs, 
and clouds, and is precipi- 
tated upon the earth as dew, 
rain, hail, and snow. It is 
absorbed by the soil and 
rocks, while in crystalline 
structures it enters into 
closer combination as water 
of crystallization. 

40. Preparation. — It is 

not necessary to prepare 
water chemically, owing to its great abundance every- 
where, but for the sake of illustration use the apparatus 
shown in Fig. 6. 

G is a hydrogen generator. 

B is a drying bulb, containing granulated calcium chloride. 

II is a bell jar. The hydrogen jet burning in this jar unites with the 
oxygen of the air, producing water, which soon collects, and falls down 
in drops. Student, write the equation and a description of the apparatus 
and manipulations. 




Fig. 6. 



HYDROGEN AND OXYGEN COMPOUNDS. 



41 



Water is formed when hydrogen is passed through a heated tube con- 
taining metallic oxides, such as copper oxide. . 

41. Question. — What is the chemical composition of water, 
and what its formula? 

We may determine the composition of water, first by 
analysis, and then, if possible, by synthesis. The experi- 
ment described on page 34 showed that when water is 
decomposed by the electric current, it yields only hydro- 
gen and oxygen, and these in the proportion of 2 vol- 
umes of hydrogen to 1 of oxygen. Knowing the relative 
weights of the gases, we see that they are obtained from 
water in the proportion of 1 part by weight of hydrogen 
to 8 of oxygen, or 2 of hydrogen to 16 of oxygen. 

Sug. Student, show that this statement is correct. 

To prove that hydrogen and oxygen alone are necessary 
to form water, and that they are present in the proportions 
found by analysis, we may cause the two gases to unite as 
follows : — 

Exp. 30 tp. The apparatus shown in Fig. 7 is called Ure's 
Eudiometer. The graduated limb and part of the plain limb 
are filled with mercury ; then, by means of a 
curved tube, 10 divisions of the graduated 
limb are filled with pure oxygen ; then fill 
say 25 more with pure hydrogen. An elec- 
tric spark is now passed through the wires 
attached to the graduated limb, while the 
thumb is held firmly over the plain limb. 
20 divisions of hydrogen will unite with 10 
divisions of oxygen; i.e., 2 of hydrogen to 
1 of oxj^gen. * IG> '" 

Query. After passing the spark, where is the water to be seen ? 

N.B. Before passing the spark, see that the plain limb is not entirely 
full of mercury, and hold the thumb as firmly as possible. 




42 



HYDKOGEN AND OXYGEN COMPOUNDS. 



Sug. Student, examine this apparatus, and write a full description of 
it and the experiment. ■ 

We see, thus, that the analysis and synthesis of water 
both lead us to the conclusion that in it hydrogen and 
oxygen are united in the proportions above stated, and 
these proportions are expressed in the formula H 2 0, the 
full significance of which cannot be explained at this 
stage. For the present, suffice it to say that formulae 
express primarily the composition of bodies by weight. 
Hereafter, we shall see that they also have to deal with 
the volumes of bodies when in the form of a gas. 

Peob. How many grams of O in 100s of H 2 ? How many of H ? 

42. The Oxy-Hyclrogen Blow-Pipe. — Small laborato- 
ries will not be likely to contain this apparatus; but, 
owing to its great value and the frequent references 
made to it, the student should become acquainted with 
it. 

The oxygen and hydrogen holders are not shown in this 
cut (see App.). They may be provided with safety- 
valves, to prevent the flow of the gas from one to the 
other. 

J is a jet containing a jet within, 
a space being left between the inner 
jet and the outer one for hydrogen to 
pass through. 

H is a stop-cock to admit hydro- 
gen into this space. O is a stop-cock 
to admit oxygen into the inner jet, 
which is not quite so long as the outer 
jet. By this arrangement the two gases 
are thoroughly mixed upon issuing into 
the air. 

C is an adjustable cup for holding 
a piece of chalk in the flame, when 
the design is to produce the brilliant 
Fig. 8. calcium light 




HYDBOGEN AND OXYGEN COMPOUNDS. 43 

The heat of the flame of this blow-pipe is intense 
enough to melt most of the refractory metals. 

The calcium light is equaled only hy the electric light. 

43. Properties of Water. — Water is an almost univer- 
sal solvent , consequently, pure water does not occur in 
nature. Snow and ice waters are nearly pure, but they 
ytill contain dust, and various gases found in the air. 
Lake Superior water is also very nearly pure, since the 
bed of the lake is composed of the old Azoic rocks whicli 
are but slightly soluble, and the lake is fed with ice, snow, 
and rain. Sea water contains about thirty known ele- 
ments in solution. 

Water is at its maximum density at +4° Centigrade. 
tVhen the temperature passes either above or below this 
point, water expands. This is a most fortunate provision, 
as otherwise, ice would be heavier than water and would 
sink to the bottom ; thus, many of our lakes and rivers 
might be frozen solid to their beds, and the summer sun 
would not suffice to thaw them. Aquatic plants and 
animals could not exist, and our temperate zones would 
become uninhabitable. 

Query. Why does the pail burst when the water freezes in it q 

Exp. 31 op. Place a thermometer through an opening in the 
ice of a frozen lake. At any depth it will read nearly +4° C. 

Query. What deductions may be derived from this experiment ? 

The Latent Heat of Water is 7 'J Calories or Thermal 

Units. 

Illustrate this statement, thus : - — 

Exp. 32 op. Mix l k of ice at 0° C. with l k of water at 79° 
C. The ice will melt, and the temperature of the 2 k of water 



44 HYDROGEN AND OXYGEN COMPOUNDS. 

will be 0° C. Hence we see that the 79 thermal units contained 
in the kilogram of water have disappeared while melting the ice, 
or, in other words, have become latent. When water freezes, 
it gives off its latent heat. 

Query. What effect, upon the temperature of a room, would be pro- 
duced by a tank oi freezing water. 

The Latent Heat of Steam is 536 Thermal Units. 

To illustrate this, proceed thus : ■ — 

Exp. 33 op. Into 5.36 k of water at 0° C. pass steam at 100° 
C. until the water boils. You will then have 6.36 k of water at 
100° C. Now, since l k of steam has parted with sufficient latent 
heat, while condensing to water (of the same temperature, i.e., 
100°), to raise 5.36 k of water 100°, or 536 k 1°, we have measured 
its latent heat, which is 536 thermal units. 

Note. Experiments 32 p and 33 p involve quite large experimental 
errors. 

When steam condenses to water it gives off all its latent 
heat ; hence its great usefulness for heating dwellings, etc. 

Drinking -Water. 

Drinking-water is apt to contain many impurities, 
organic and inorganic, some of which are believed to be 
very deleterious to health, frequently leading to various 
forms of disease, such as typhoid fever, etc. 

Query. How does drinking-water become contaminated with impuri 
ties? 

Let the student make the following tests upon drink- 
ing-water obtained from his own well, or from the usual 
source of water for drinking purposes. 



HYDROGEN AND OXYGEN COMPOUNDS. 4o 



Tests for Impurities in Drinking- Water. 

Exp. 34 p. For Organic Impurities. — Fill a tall glass jar 
with the water to be tested. Add a few drops of sulphuric 
acid, H0SO4 ; then add a solution of potassium permanganate, 
RM11O4, until the whole assumes a deep purplish tint. Stand 
in a warm place for one hour. If organic impurities are 
present, the solution will be decolorized. 

Another Test. — When much organic matter is present. — 
Fill a tightly-stoppered bottle nearly full of the water to be 
tested. Set in a warm place for several days. An offensive 
odor indicates organic impurities. Such impure water ^ it is dan- 
gerous to drink. A good charcoal and gravel filter will remove 
organic impurities if only a small amount be present. 

Sug. Teacher explain the construction of a filter, and how to take 
care of it. 

Test for Ammonia. 

Exp. 35 p. Distil the water hi perfectly clean glass apparatus 
(after dissolving a small quantity of sodium carbonate, Na 2 C0 3 , 
in the water to be tested) . 

Collect the distillate in tall glass jars in volumes of 50 cc 
each, numbering them successively 1, 2, 3, 4, etc. 

Add about 2 CC of Nessler's Test Solution (see App.) to 
each of these jars. If ammonia be present in any or all of 
inem, such as contain it will be tinged brownish-yellow. 

N.B. Drinking-water containing much ammonia is unfit to drink, 
since the presence of ammonia indicates that the water of the well lias 
percolated through decaying vegetable or animal substances. 

Test for Chlorine or Chlorides. 

Exp. 36 p. Concentrate 50 cc of water to be tested to 25. 
Acidulate with nitric acid ; then add a few drops of a solution 
of silver nitrate, AgN0 3 . If a white precipitate is made which 



46 HYDROGEN AND OXYGEN COMPOUNDS. 

is soluble in ammonia, NH 4 OH, and insoluble in nitric acid, 
HN0 3 , chlorine is present. 

The presence of much chlorine is to be looked upon 
with suspicion (as sewage water always contains chlorine 
in considerable quantities), unless in the vicinity of salt 
wells or of the ocean. 

Test for Nitrites. 

Exp. 37 p. Place the solution to be tested in a test tube 
and then add a few drops of a solution of sulphanilic acid ; 
next add a few drops of a solution of naphthylamine chloride ; 
now acidulate the whole with hydrochloric acid. If nitrites 
be present, the solution will turn rose-red. 

Note. Nitrites will also bleach a solution of potassium permanganate, 
KMn0 4 , when acidulated with sulphuric acid, H 2 S0 4 ; but this test is not 
reliable, since organic matter acts in the same way. 

The presence of nitrites is an indication of sewage, 
especially when chlorides and ammonia are present. 

Too much stress cannot be laid on the danger of drink- 
ing water contaminated with sewage. Fevers and pesti- 
lence may follow its use. 

Test for Hydrogen Sulphide, H 2 S. 

Exp. 38 p. Acidify, with sulphuric acid, H 2 S0 4 , about l 1 of 
the water to be tested. Place it in a stoppered flask holding 
say 2 1 . Suspend above the liquid a strip of bibulous paper 
moistened with lead acetate, Pb (C 2 H 3 2 ) 2 - Cork tightly, and 
set in a warm place for several hours. Hydrogen sulphide, if 
present, will blacken the paper. 



HYDROGEN AND OXYGEN COMPOUNDS. 47 



Test for Hardness. 

Exp. 39 p. Employ Clark's Soap Test thus : Place 100 cc of 
the water to be tested in a stoppered glass flask. Add l cc of 
Clark's Soap Solution; then shake thoroughly. If a perma- 
nent lather be not formed, again add l cc of the soap solution, 
and shake as before, and thus proceed until a permanent lather 
remains, for three minutes, unbroken over the surface of the 
water. (See App. for Clark's Soap Solution.) 

The number of cubic centimetres of soap solution added 
less 1^ will be equal to -^ the parts per million of hardness, 
or to Jq- the number of milligrams of hardness, per litre. 

Hardness is usually caused by the presence of calcium 
and magnesium compounds. 

Xote. Hardness and hydrogen sulphide do not necessarily impair the 
qualities of drinking-water ; on the contrary, they often serve useful pur- 
poses. 

Hydrogen Dioxide, H 2 2 . 

44. Preparation. — Hydrogen dioxide does not occur 
in nature in quantity, though it is present in small 
amounts in the air, and in rain and snow. It may be 
prepared chemically in several ways, of which we give only 
one, the best way. 

Exp. 40 p. Treat pulverized barium dioxide with dilute sul- 
phuric acid (5 parts water to 1 part acid) in a beaker. Stir 
thoroughly to bring all the barium dioxide in contact with the 
acid. A white precipitate, barium sulphate, BaS0 4 , will settle 
to the bottom upon standing, and the clear fluid will contain 
the hydrogen dioxide. This separation can be effected more 
quickly by filtering. The clear fluid which comes through con- 
tains the hydrogen dioxide in dilute solution. The reaction 
may be expressed thus : Ba0 2 + H 2 S0 4 = BaS0 4 + Ho0 2 . 



48 HYDROGEN AND OXYGEN COMPOUNDS. 

Prob. How many grains H 2 2 may be obtained from 10» Ba0 2 ? 

This dilute solution of hydrogen dioxide may be con- 
centrated by allowing it to stand in a beaker placed over 
strong sulphuric acid in the vacuum of an air-pump ; but 
after and during concentration, it should be kept at a low- 
temperature. 

45. Properties. — Hydrogen dioxide is a volatile, un- 
stable liquid, slowly separating into water and oxygen at 
low temperatures (student, write the equation). When 
heated, unless care be used, it explodes with violence. 

It is syrupy, transparent, and colorless, possessing a very 
nauseating and stringent taste, and an acid reaction. 

Its specific gravity is 1.497, and it has not been frozen. 

Aqueous hydrogen dioxide is sold commercially for 
bleaching old engravings and paintings. It is also used 
to change dark hair to lighter shades, which is a danger- 
ous practice, since it is an active poison when brought 
upon the skin, often producing white blisters which finally 
become very painful. 

46. Test for Hydrogen Dioxide. — Acidulate a small 
quantity of a solution of hydrogen dioxide (or the liquid 
to be tested) with two or three drops of sulphuric acid, 
H 2 S0 4 , in a test-tube. Add a small quantity of ether, 
(C 2 H 5 ) 2 0, also five or six drops of potassium chromate, 
K 2 Cr0 4 ; shake well. Hydrogen dioxide, when present, 
turns the whole to a splendid blue color. On standing, 
the ether absorbs this color, and separates out in a blue 
layer. This color is due to perchromic acid, H 4 Cr0 7 , 
which soon decomposes. 



HYDROGEN AND OXYGEN COMPOUNDS. 49 



SUMMARY OF STUDENT'S WORK IN H, H 2 0, AND H2O2. 

1. Make the experiments as indicated. 

2. If the laboratory contain an oxy-hydrogen blow-pipe, teacher and 
students should use it in making the calcium light, fusing bits of metals 
as Fe, Au, Pt, etc. 

3. Art. 43. Draw up reports giving results of the Exp. 34 p- 39 p. 
This is work sufficient for a whole week. 

4. Albuminoids may be detected thus : Add solid KOH to the water 
until strongly alkaline, and boil a short time. Now pour into a retort and 
add K Mn O4, and distil, collecting and testing the first portions of dis- 
tillate as in Exp. 35 p, since albuminoids thus treated yield ammonia. 

5. Read Wanklyn's Water Analysis. In case it is desirable to de- 
termine the amounts of ammonia, etc., present in drinking-water, complete 
directions are to be found in this work. One should hesitate to pronounce 
upon the potableness of drinking-water without first making quantitative 
determinations. 

G. Prob. The imperial gallon contains 70,000 gr. of distilled water; 
the U. S. gallon contains 58,328.88 gr. How many grains of hardness 
per U. S. gallon does the sample of water that you have analyzed contain ? 
How many grains per imperial gallon does it contain? 

7. Try to remove, by boiling, the hardness from a sample of water. In 
case you succeed, the hardness is said to be temporary ; and it is due to the 
presence of calcium carbonate, CaC0 3 , and perhaps magnesium carbonate, 
MgC0 3 . Should you not succeed in thus removing it, the hardness is 
called permanent, and probably consists of the sulphates of calcium and 
magnesium. 

Query. How can you determine if both permanent and temporary 
hardness be present ? 

8. Pkob. How many grams can be obtained by decomposing 100 cc 
of water (l cc = Is) 1 ? How many grams H ? 

9. Pkop>. In the equations enclosed by parentheses, assume 10s of 
the first substance, and ascertain how many grams will be required of the 
remaining substances. 

10. Art. 44. It is not necessary to condense H 2 2 in vacuo, unless a 
concentrated solution is required. 

Student test H 2 2 , as in Art. 46. A dilute solution of H 2 2 will answer 
well for this purpose. Use K 2 Cr 2 7 , also, in place of lv 2 Cr0 4 . Do yon 
obtain the same color as before 1 



CHAPTER III. 

NITROGEN. — ITS OCCURRENCE, ETC. — AMMONIA. — OXIDES 
OF NITROGEN. — THE NITROGEN ACIDS. — HYDROXYLA- 
MINE. 

NITROGEN. 

Symbol, N"'. — Atomic Weight, 14 ; Sp. Grav., 0.9713. 

47. Occurrence. — Nitrogen occurs free in the atmos- 
phere, of which it constitutes nearly four-fifths by volume, 
or 77 per cent by weight. It also occurs in many chemical 
compounds, such as potassium nitrate, KN0 3 ; sodium 
nitrate, NaN0 3 ; ammonia, NH 3 ; and in many organic 
substances, particularly those of animal origin. 

48. Preparation. — Exp. 41 t. Place in an iron sand- 
bath about 2 g of phosphorus ; ignite the phosphorus, and float 
the sand-bath on the water in a pneumatic trough. Immedi- 
ately place over the burning phosphorus a bell-jar of about 
4 1 capacity, allowing the mouth of the jar to be under water, 
so that no outside air can enter. The phosphorus enters into 
combination with the oxygen of the air contained within the 
jar, forming dense white fumes of phosphorus pentoxide, 
P 2 5 , and perhaps of the trioxide, P 2 3 . In a short time 
these fumes settle, and are dissolved by the water, leaving the 
nitrogen nearly pure. 

Nitrogen may be prepared in many ways, but the 
method above indicated is a cheap and convenient one 
for laboratory use. 



NITROGEN. 51 

49. Properties of Nitrogen. — Exp. 42 p. Bend a small 
glass tube in the shape of a letter V, and draw out one extrem- 
ity into a jet. Now insert the plain end of the tube into the 
jar of nitrogen obtained in Exp. 41, and press the jar down 
into the water of the pneumatic trough until the nitrogen issues 
through the jet. Try to ignite the gas. Does it burn? 

Exp. 43 p. Fill with nitrogen a large test-tube. Insert a 
glowing match ; a burning match ; a lighted taper. What results ? 

Exp. 44 p. Try to fire the hydrogen pistol when filled with 
a mixture of nitrogen and common air. What occurs ? 

Nitrogen is a gaseous element, and, like hydrogen and 
oxygen, none of its physical properties render it percep- 
tible to sight, taste, or smell. Its specific gravity is 0.971 ; 
and l 1 at 0° C. and 760 mm pressure weighs 1.256s. 

Chemically considered, it is not an active element, as 
shown by the apathy which it exhibits in entering into 
combination with other elements. 

Indirectly, however, it unites with hydrogen, oxygen, 
and carbon to form important chemical compounds. 

Its greatest value in nature is clue to its mildness, and 
the remarkable persistency with which it remains in a free 
state. It thus serves to dilute the oxygen of the atmos- 
phere, which is simply a mechanical mixture of these gases, 
consisting of 23.1 parts oxygen and 76.9 parts nitrogen, 
by weight. As one would infer, it has no poisonous prop- 
erties, neither will it burn nor support combustion. 

Nitrogen is but slightly soluble in water, and has been 
condensed to a liquid at — 146° C. and under a pressure 
of 33 atmospheres. 

50. Test for Nitrogen. — Owing to its passive nature, 
nitrogen does not give any reaction whereby it may be 



52 NITROGEN AND HYDROGEN. 

readily detected when present in small quantities. Larger 
amounts are indirectly tested by the negative results 
obtained. 

NITROGEN AND HYDROGEN. 

51. Ammonia. — Nitrogen and hydrogen unite to form 
an important compound, viz. : — 

Ammonia, NH 3 . 

52. Occurrence. — Ammonia occurs free in the atmos- 
phere, being produced by the decay of organic matter 
containing nitrogen. It is also found dissolved in small 
quantities in rain water and many surface waters. Its 
compounds, such as ammonium chloride, NH 4 C1, and am- 
monium carbonate occur but sparingly in nature, although 
they are common articles of commerce, obtained by arti- 
ficial processes. Ammonia solution, or aqua ammoniae, is 
also a staple article of commerce. 

53. Preparation. — Exp. 45 p. Place in one hand a small 
quantity of dry quicklime, CaO, and in the other an equal 
bulk of pulverized ammonium chloride, NH 4 C1. Note that 
neither substance emits an odor. Now rub them together 
between the palms of the hands, and carefully smell the invisi- 
ble gas given off. It is ammonia. 

Exp. 46 p. To a solution of ammonium chloride in a test- 
tube add a few drops of potassium hydroxide, KOH. Warm 
gently, and note the fumes. Do you again obtain ammonia? 
Also try in the same way a solution of ammonium nitrate, 
NH 4 N0 3 . What result? Moisten a glass stirring-rod with 
hydrochloric acid, HC1, and hold it in the escaping vapors ; 
notice the white fumes that are formed. Try the same with 



NITROGEN AND HYDROGEN. 



53 



nitric acid, HN0 3 . What takes place is indicated in the two 
following equations : — 

1. NH3+HCI = NH 4 C1. 

2. NH 3 + HN0 3 = NH 4 N0 3 . 

Sug. Explain these equations. Do you obtain the same substances 
with which you commenced 1 

Exp. 47 t. Thoroughly mix two parts, by weight, of finely* 
pulverized, dry ammonium chloride, and one part of dry quick- 
lime. Quickly place the mix- iiiiTSUUd » 
ture in the generating-flask F 
(Fig. 9), and then add a thick 
layer of dry quicklime, which 
will serve to dry the ammonia 
as it rises through it. Insert 
the cork containing the bent 
tube, and gently heat the flask. 
Ammonia will collect in the 
bottle B. 

This method is used when 
dry ammonia gas is required. 
What occurs in the flask is 
indicated by the equation, — Fig. 9. 

CaO + 2 NH4CI = 2 NH 3 + H 2 + CaCl 2 . 

Queries. CaCl 2 is a substance called calcium chloride, and is a solid. 
Where is it to be found after the reaction ? What becomes of the water 1 
Would passing the gas through a long tube filled with quicklime tend to 
insure the dryness of the ammonia ? From the position in which the bottle 
B is held, should you judge ammonia to be lighter, or heavier, than air ? 

Exp. 48 t. Prepare thick pastes (with water) of the same 
substances used in the last experiment, employing the same 
proportions of the dry substances before moistening. Arrange 
an apparatus similar to that shown in Fig. 10. The first wash- 
bottle, A, acts as a safety-valve to prevent water from return- 




54 



NITKOGEN AND HYDKOGE2ST. 



ing into F ; also to prevent explosions. Notice that the centre 
tube alone dips beneath the water. The bottle B contains 
cold water, and serves as a condenser. In this bottle the entry 
and centre tubes extend below the surface of the water. C is 
also a bottle containing cold water. It is best to place B 
and C in vessels, and to surround them with a freezing mixture 
of snow, or pounded ice and salt. Now pour these pastes 
as rapidly as possible into F, shake quickly, and connect with 




Fig. 10. 



the wash-bottles. Apply heat to F, and boil for some time. An 
aqueous solution of ammonia will be found in B and C. 

Sug. Explain the reasons for arranging A in the manner described. 
After the experiment, note that the contents of B and C differ in no way 
from ordinary aqua ammoniae. 

The last experiment indicates the general process em- 
ployed in manufacturing commercial aqua ammoniae. 
Other methods of preparing ammonia are as follows: — 
1. Ammonia is obtained in small quantities by mixing 
nitrogen and hydrogen in a eudiometer, and by passing 
for some time a silent electric discharge. 

Query. How does this explain the production, at certain times, of 
ammonia in the atmosphere ? 



NITROGEN AND HYDROGEN. 55 

2. It is produced by allowing heaps of compost and 
urine to decompose. 

Query. How do you explain the presence of ammonia in stables ? 

Exp. 49 p. Heat in a test-tube a small ball of hair, or 
wool, or a few hoof-clippings. What is given off? 

3. Ammonia may be had by the dry distillation of such 
nitrogenous bodies as hair, hoofs, hides, and horns. It was 
formerly prepared in this way, and thus received the name 
spirits of hartshorn. 

4. In the distillation of coal to make illuminating gas, 
ammonia is formed as a by-product. In this case the 
nitrogen and part of the hydrogen contained in the coal 
are driven off, combined as free ammonia and ammonia 
compounds. These ammoniacal products are led into 
water containing hydrochloric or sulphuric acids; from 
the compounds thus formed we obtain the ammonia of 
commerce. 

54. Properties. — Exp. 50 p. Place in a generating-tlask 
a concentrated solution of ammonia ; pass through this solution 
a current of oxygen gas. The escaping mixture of ammonia 
and oxygen will burn, at the mouth of the flask, with a yellowish 
flame. Under ordinary conditions, ammonia does not burn. 

Sug. Student, try to light a jet of NH 3 . 

Exp. 51 p. Heat to bright redness a long spiral coil of 
platinum wire, and quickly introduce it into the mouth of a 
common reagent bottle containing a strong solution of am- 
monia. The wire will continue to glow while the ammonia is 
decomposed, thus : — 

2NH 3 + 30 = NH 4 N0 2 + H 2 0. 

Queries. How do you account for this phenomenon ? Whence comes 
the O indicated in the above equation ? 



56 NITROGEN AND HYDROGEN. 

The composition of ammonia gas may be determined by 
introducing the dry vapor into the graduated limb of lire's 
eudiometer, and passing a succession of electric sparks, 
when the- volume of the enclosed gas is doubled. This 
may now be proven, by introducing oxygen and exploding, 
to consist of one volume of nitrogen and three volumes of 
hydrogen. 

We may here learn a useful fact; viz., that the formula 
X2~ 3 . in addition to its other significations, also represents 
two volumes of ammonia in the form of a gas; and the same 
is true of all formulas representing gases. 

The name ammonia originated from the fact that the 
gas was first prepared from sal-ammoniac, NH 4 C1, a sub- 
stance formerly confounded with the salt, NaCl, produced 
near the ruins of the temple of Jupiter Amnion, in Lybia. 

Ammonia is an invisible gas possessing a powerful, irri- 
tating odor, and intensely alkaline properties. 

Bug. Try the effect of ammonia upon a strip of moist, red litmus paper 

This gas is very soluble in water, l cc of water at 0° C. 
absorbing 1148 cc of ammonia ; and l 1 at 0° and 760 mm pres- 
sure weighs 0.762*. It can easily be condensed to a liquid 
under a pressure of 7 atmospheres at + 15.5° C. ; and this 
liquid, on being cooled to — 75° C, becomes a transparent 
solid. 

In passing from a liquid to a gaseous state, gases always 
absorb a large amount of heat. M. Carre has taken advan- 
tage of this fact in constructing an ice machine. (Fig. 11.) 

B is a boiler containing a strong solution of ammonia. C is 
a condenser with an air-tight space between its double walls. 
the whole being surrounded by the non-conducting covering, H. 
B is gradually warmed over a slow fire, while C is placed in 
a vessel of cold water. The ammonia of the aqueous solution 



NITROGEN AND HYDROGEN. 



57 




in B is driven into the air-tight space in C, where it is con- 
densed by its own pressure. Water is now placed in C, and 
B is subjected to a cold bath, 
when the liquid ammonia in the 
walls of C quickly evaporates, 
and is absorbed by the cold 
water in B. This evaporation 
abstracts so much heat from 
the water in C that it is soon 
frozen. 

Exp. 52 p. Place in a beaker 
glass a dilute solution of nitric 
acid, HN0 3 ; now carefully add _1|||||||||L 
ammonia until the solution is 
neutralized so that it does not 
affect litmus paper. Gently evaporate this solution to dryness, 
when a crystalline salt is obtained. 

Ammonia unites with acids to form salts, and is known 
as the volatile alkali. This action with acids may be> 
illustrated by the equations: — 

NH3 + HCI = NH 4 C1. 
NH 3 + HNO3 = NH 4 N0 3 . 

It will be seen that the ammonia, NH 3 , is added directly 
to the acid. The compounds thus formed are called 
ammonium compounds, the group NH 4 contained in them 
leing known as ammonium. 

Since ammonia neutralizes an acid, it is used in cases of 
accidents when acids are spilled upon the clothes or flesh. 
But should the acid be received in the face, it is best to 
wash it off quickly with much water, then with a weak 
solution of ammonia, and finally, without rubbing, to cover 
the injured parts with sweet oil. 



58 NITROGEN AND GXYGEN. 

Ammonia produces a stimulating effect upon the human 
system when inhaled, and is often employed in cases of 
fainting, or where over-doses of chloroform, laughing gas, 
ether, etc., have been taken. It also neutralizes the effects 
of such poisonous or irritating gases as chlorine, sulphur 
dioxide, and nitrogen tetroxide. 

55. Tests for Ammonia, NH 3 . — 1. When present in 
very small quantities, as in drinking-water, ammonia is 
best detected by means of Nessler's test solution. (See 
App.) 

2. When present in considerable quantities, add to the 
solution to be tested potassium hydroxide, KOH, and 
warm gently. Ammonia, if present, is driven off, and may 
be recognized as follows : — 

(a) By its pungent smell. 

(5) By turning moistened red litmus paper blue. 

(e) A warm glass rod previously moistened in hydro- 
chloric acid, HC1, is coated white by ammonia gas. Char- 
acteristic white fumes (NH 4 C1) are also produced when 
much ammonia is present. 

NITROGEN AND OXYGEN. 

56. Nitrogen indirectly unites with oxygen to form five 
oxides or compounds, viz. : — 

N 2 0, Nitrogen Monoxide or Nitrous Oxide. 

NO, (or N 2 2 ) Nitrogen Dioxide or Nitric Oxide. 

N 2 3 , Nitrogen Trioxide or Nitrous Anhydride. 

N0 2 (or N 2 4 ), Nitrogen Tetroxide. 

N 2 5 , Nitrogen Pentoxide or Nitric Anhydride. 



NITROGEN AND OXYGEN. 



59 



Nitrogen Monoxide, N 2 0. 

57. Occurrence. — This substance is a gas, and never 
occurs free in nature. It is often known by the common 
name of nitrous oxide. 

58. Preparation. — Exp. 53 p. Place in a test-tube a 
small quantity of ammonium nitrate, NH 4 N0 3 , and heat 
gently in the Bunsen flame. Note the sweetish odor. The 
gas thus obtained is nitrogen monoxide. Insert a glowing 
match, as in testing for oxygen ; also try a burning match. 

Queries. How does this gas behave, in comparison with oxygen 1 
How can you distinguish it from oxygen ? 




FeS0 4 KOH 

Fig. 12. 



H 9 



Exp. 54 t. Place 20 g ammonium nitrate, NH 4 N0 3 , in a 
generating flask, and connect with three wash-bottles, as 
shown in Fig. 12. The thistle-top tube contains a small quan- 
tity of mercury, and will serve as a very efficient safety-valve. 
A moderately strong heat will serve to decompose the contents 
of the flask, thus : — 

NH 4 N0 3 = N 2 + 2H 2 0. 

But the nitrogen monoxide may contain impurities such as 
nitric oxide, NO, and chlorine. It is accordingly washed through 



60 NITROGEN AND OXYGEN. 

a solution of ferrous sulphate, FeS0 4 , which is placed in the 
first wash-bottle, to remove the nitric oxide. The second wash- 
bottle contains a solution of potassium hydroxide, to remove the 
chlorine ; while the third bottle contains water. The contents 
of the bottles must be warm, since nitrous oxide is somewhat 
soluble in cold water, and but slightly so in warm solutions. 
The gas thus prepared is best collected in rubber gas-bags, 
where it may be kept for experimental purposes in studying its 
properties. 

Nitrogen monoxide may be prepared by other methods ; 
buu the one given above is always used in its practical 
preparation. 

59. Properties. — Exp. 55 op. Inhale a small quantity of 
pure nitrogen monoxide, as prepared above, and note its odor, 
and taste. 

Sua. Student, make the same experiments with nitrogen monoxide as 
with oxygen. 

Nitrogen monoxide is a colorless gas possessing a pleas- 
ant smell and sweetish taste, and when mixed with air, and 
inhaled, produces a peculiar intoxication, while conscious- 
ness remains, whence it derived its name "Laughing Gas." 
When inhaled in a pure state, it affects the system thus: — 

1. Intoxication and singing in the ears are experienced. 

2. Insensibility follows. 

3. If continued long enough, death ensues. 

This gas is chiefly used for anaesthetic purposes, by den- 
tists and physicians, who keep it stored under pressure in 
tanks or cylinders. 

It is soluble in water, 100 cc of water at 0° dissolving 130 C€ 
of nitrogen monoxide, while alcohol dissolves still greater 
quantities. 

This gas can be liquefied at 0° by a pressure of 30 atmos- 



NITROGEN AND OXYGEN. 



61 



pheres, or at ordinary pressures by reducing its tempera- 
ture to — 88° C. By mixing this liquid with carbon 
bisulphide, CS 2 , and by placing the mixture in a receiver 
from which the air and vapors are afterwards rapidly 
exhausted, the remarkably low temperature of — 140° C. 
has been reached. 

Nitrogen monoxide will support combustion ; but in order 
to initiate the process, some substances, as sulphur, must 
be freely burning. Ignited sodium, potassium, and phos- 
phorus, however, burn in it quite as briskly as in oxygen. 

The specific gravity of this gas is 1.527; and l 1 at 0° and 
760 mm weighs 1.972*. 

60. Tests for Nitrogen Monoxide, N 2 0. — This gas 
closely resembles oxygen, from which it is easily distin- 
guished, first by its odor and taste, and second bj 7 its great 
solubility in cold w T ater. 

Nitrogen Dioxide, NO. 

61. Preparation. — This oxide of nitrogen, also called 
nitric oxide, does not occur free in nature. 

Exp. 56 p. Place copper filings in the generating-flask A * 
then adjust the cork with the tubes B and C, as shown ic 
Fig. 13. Now, through the tube B, introduce into A dilute 
nitric acid (sp. grav., 1.2). 
At first A will be filled 
with reddish - brown fumes ; 
but these disappear as soon 
as the air is expelled from 
the apparatus, and a color- 
less gas, NO, collects in G. 
Note the disagreeable odor. 
Allow some of the gas to 
escape into the air. What 
do you observe ? % Fig. 13. 




62 NITROGEN AND OXYGEN. 

Nitrogen dioxide can be prepared from nitric acid by 
the action of other metals than copper, such as iron, zinc, 
silver, and mercury. It might be well to know, however, 
that this gas thus prepared contains impurities such as 
nitrogen and nitrogen monoxide ; but these impurities are 
insignificant in qualitative work. The reaction with cop- 
per is expressed thus : — 

3 Cu + 8HN0 3 = 3 Cu (N0 3 ) 2 + 4H 2 + 2 NO. 

62. Properties. — Nitrogen dioxide is a colorless gas, 
but when brought in contact with the air, it unites with 
atmospheric oxygen to form the reddish-brown fumes ? 
N0 2 , seen at the beginning of the last experiment. 

Iron, potassium, and phosphorus, when very strongly 
ignited, will burn in this gas, but not so readily as in 
nitrogen monoxide, since it does not decompose as readily 
as the latter gas, to supply oxygen for the purpose of 
combustion. What takes place when bodies burn in these 
oxides of nitrogen may be seen from the following equa- 
tions : — 

1. N 2 + 2K = K 2 + 2N. 

2. NO + 2K=K 2 0+N. 
Sug. Try NO with a glowing match. What result ? 

Nitrogen dioxide was formerly considered as an incon- 
densible gas, but it became a liquid at — 11° undo* 
104 atmospheres. 

The specific gravity of this gas is 1.038 ; and l 1 under 

'standard conditions weighs 1.343 g . 

Query. At what temperature ^nd pressure have we given the weights 
of the gases up to this time 2 

63. Tests for Nitrogen Dioxide, NO. — - 1. We can 

distinguish this gas by the brownish-red fumes which it 
gives upon escaping into the air. 



NITROGEN AND OXYGEN. 63 

2. When passed into a solution of ferrous sulphate, FeS0 4 , 
the solution turns brown. 

Note By heating this solution, chemically pure NO may be obtained- 

Nitrogen Trioxide, N 2 3 . 

64. Preparation. — This gas also does not occur in 
nature. The following is the best method of preparing 
it: — 

Exp. 57 p. To a few grains of starch in a test-tube add 
reagent nitric acid, HN0 3 , and gently heat in the Bunsen flame. 
Dark-reddish fumes of the trioxide are given off. 

Exp. 58 p. Place in a generating-flask 10 g of starch, and 
cover with nitric acid. Cork the flask tightly with a rubber 
stopper, carrying a bent delivery-tube, which projects into 
another flask filled with cold water and surrounded by a mix- 
ture of ice and salt. Gently heat the generating-flask con- 
taining the starch and nitric acid, when the trioxide is plen- 
tifully produced, and absorbed by the cold water with which 

it unites, thus : — 

N 2 3 + H 2 = 2 HN0 2 , 

nitrous acid being formed by this union. Also, pass a portion 
of the nitrogen trioxide into a cold solution of potassium 
hydroxide, when potassium nitrite will be formed, thus : — 

2 KOH + N 2 3 = 2 KN0 2 + H 2 0. 

Preserve the above for work under nitrous acid. 

Nitrogen trioxide is of itself unimportant, except as being 
the starting-point from which nitrous acid and its com- 
pounds are formed. Consequently we will again refer to 
it, omitting its tests, etc., for the present, since they are 
the same as for nitrous acid. (Art. 72.) 



64 NITROGEN AND OXYGEN. 

Nitrogen Tetroxide, N0 2 (or N 2 4 ). 

65. Preparation, etc. — This oxide of nitrogen is unim- 
portant, and is easily obtained by artificial processes, e.g., 
when lead nitrate, Pb(N0 3 ) 2 , is heated in a hard glass 
retort, dense reddish fumes of the tetroxide are evolved,, 

thus : — 

Pb(N0 3 ) 2 = PbO + 2 N0 2 + O. 

These fumes can be condensed by passing them into a 
U-tube surrounded by a freezing mixture. When passed 
into water, the following reaction occurs : — 

2 N0 2 + H 2 = HN0 2 + HN0 3 . 



Nitrogen Pentoxide, N 2 5 . 

66. Preparation, etc. — Nitrogen pentoxide is a white 
crystalline solid assuming the form of rhombic crystals or 
six-sided prisms. Although from a scientific standpoint it is 
an important compound, being the anhydride of nitric acid 
(by anhydride of an acid Ave mean a certain oxide that, 
uniting with water, produces that acid), it is, nevertheless, 
so unstable, and difficult of preparation, that it is not 
advisable to attempt its production in small laboratories. 
There are several methods of obtaining the pentoxide, one 
of which is by passing dry chlorine gas through a glass 
tube containing silver nitrate. The reaction occurs in two 
stages, thus : — 

1 . AgN0 3 + 2 CI = NOoCl + AgCl + O. 

2. N0 2 C1 + AgN0 3 = N 2 O s + AgCl. 

The pentoxide unites with water, thus r — 
N 2 5 + H 2 = 2HN0 3 . 



nitrogen and oxygen. 65 

The Compounds of Nitrogen, Oxygen, and Hydro- 
gen ; or, the Nitrogen Acids. 

67. There are three acids in this series, viz. : — 

1. Hyponitrous Acid, H 2 N 2 2 . 

2. Nitrous Acid, HN0 2 . 

3. Nitric Acid, HN0 3 . 

None of these acids occur free in quantity, but all of 
them have now been prepared in the free state. It is 
interesting to note the manner in which these acids may 
be supposed to originate from the union of their anhy- 
drides with water, thus : — 

N 2 + H 2 = H 2 N 2 2 . 

N 2 3 + H 2 = 2 HN0 2 . 

N 2 5 + H 2 = 2HN0 3 . 

Query. Can they all thus be produced ? 

Hyponitrous Acid, H 2 N 2 2 , and Hyponitrites , 

68. Preparation. — Hyponitrous acid is obtained when 
hydroxylamine sulphate acts on sodium nitrite, and its 
compounds (called hyponitrites} with certain metals are 
known. 

Exp. 59 p. Add sodium amalgam to a strong solution of 
potassium nitrate in a beaker, until hydrogen gas escapes. 
Potassium hyponitrite will be formed, thus : — 
KN0 3 + 4H- KNO + 2 H 2 0. 

Queries. Is the above solution alkaline ? Whence comes the H of 
the above reaction '? 

Retain the solution thus prepared to make the follow- 
ing : — 

69. Tests for Hyponitrites. — 1. Hyponitrites in alka- 
line solutions precipitate lead hyponitrite, Pb(NO) 2 , upon 



66 NITROGEN AND OXYGEN. 

addition of lead acetate, Pb(C 2 H 3 2 )2. This precipitate is 
white, changing to yellow. 

Pb(C 2 H 3 2 ) 2 + 2KNO = Pb(NO) 2 + 2K(C 2 H 3 2 ). 

2. Hyponitrites in alkaline solutions do not turn a solu- 
tion of starch paste and potassium iodide, KI, blue, while 
acid solutions (use acetic acid to acidulate) do effect this 
change. 

8. In solutions acidulated with acetic acid they bleacl 
a solution of potassium permanganate, K'Mn0 4 . 

4. Upon adding silver nitrate to a nearly neutral hypo 
nitrite solution, silver hyponitrite, AgNO, a yellow pre- 
cipitate, is thrown clown. 

KNO + AgN0 3 = AgNO + KN0 3 . 

Nitrous Acid, HN0 2 , and Nitrites. 

70. Preparation. — Nitrous acid is a very unstable com- 
pound; but its salts, called the nitrites, are stable and well 
known. It may be prepared by the action of nitrogen tri- 
oxide upon water. (Art. 64.) 

Query. How can you obtain a nitrite % 

71. Properties. — Nitrous acid, upon standing or upon 
being heated, undergoes decomposition, thus: — 

3 HN0 2 = HN0 3 + 2 NO + H 2 0. 

The nitrites are all soluble in water ; and since they are 
produced upon the surface of the earth by the transforma- 
tions of decaying nitrogenous substances, they will be 
found in drinking water contaminated with sewage. (See 
Exp. 37.) 

All nitrites deflagrate when thrown upon hot charcoal, 
and they are decomposed by the action of stronger acids, 
giving off fumes of nitrogen trioxide, N 2 3 . 



NITKOGEN AJND OXYGEN. 67 

Experimental Problem. Given: Starch, nitric acid, and potassium 
hydroxide. Prepare, and test as you proceed, 1st, N 2 3 ; 2d, HN0 2 ; 3d. 
KNO s j 4th, X 2 3 ; using in each case the last substance produced to obtain 
the next succeeding compound. 

72. Tests for Nitrous Acid and Nitrites. — 1. Free 
nitrous acid turns a solution of starch paste and potassium 
iodide blue. 

2. It bleaches a solution of potassium permanganate. 

3. In solutions acidified with acetic acid, the nitrites 
bleach a solution of potassium permanganate. When 
acidulated with acetic acid, they give a white precipi- 
tate, AgNOo, with silver nitrate. Also see Exp. 37. 

Exp. Prob. Let the student have two unlabelled solutions, one a nitrite 
and one a hyponitrite ; then let him determine which is the nitrite. 



Nitric Acid, HN0 3 , and the Nitkates. 

73. Occurrence and Preparation. — Free nitric acid 
barely occurs in nature ; but its compounds, as potassium 
nitrate, KN0 3 , or saltpetre, and sodium nitrate, NaN0 3 , or 
Chili saltpetre, are found in large quantities. 

Exp. GOt. Place in the retort A (Fig. 14) equal parts, by 
weight, of strong sulphuric acid and pulverized potassium 
nitrate. Surround the receiver R with snow or ice, or allow 
a stream of cold water continually to flow over it. Applv heat 
to A, which rests upon a piece of wire gauze, when nitric acid 
will be given off and condensed in R. As soon as the opera 
tion is finished, pour the acid into a glass-stoppered bottle, 
and reserve for a few experiments which will be given under 
" Properties." 

Nitric acid thus prepared is apt to be colored, owing to 
the presence of some of the lower oxides of nitrogen; but 
chemically pure nitric acid is colorless. The commercial 



68 



NITROGEN AND OXYGEN. 



acid is prepared on the large scale by treating Chili salt- 
petre, NaN0 3 , in iron retorts with sulphuric acid, the vapors 
being condensed in stoneware condensers. The acid is 
afterwards purified by distillation. If much water be 
present, a weak acid is at first obtained; if little water.be 
present, a stronger acid distils over ; but in either case an 
acid of the specific gravity of 1.4 is finally obtained. 

74. Properties. — Exp. 61 t. Place in an evaporating dish 
2 CC or 3 CC of the strong acid obtained above. With the aid of 
a long-handled deflagrating spoon, drop in a small piece of 




Fig. 14. 



phosphorus. It usually takes lire, and that, perhaps, with 
explosive violence. There is some danger attendant upon this 
experiment. 

Exp. 62 p. Heat to redness some finely-powdered charcoal 
in an iron sand-bath. A few drops of strong nitric acid wil 
cause the charcoal to deflagrate. 

Nitric acid is an exceedingly powerful oxidizing agent 
owing to the ease with which it gives up a part of its oxy- 
gen. This oxygen, when in a nascent condition, that is, at 
the moment it is liberated, is by far more active chemi- 



NITROGEN AND OXYGEN. 69 

cally than when in a free condition. We may here note 
that the same is true of all elements when in a nascent 
state. 

Exp. 63 p. Ignite a small quantity of spirits of turpentine 
in an evaporating dish by carefully adding a few drops of a 
mixture of equal parts nitric and sulphuric acids. 

Nitro-glycerine is prepared by treating common glycerine 
with these acids, at low temperatures. What is dynamite? 

Exp. 64 p. Sprinkle upon red-hot charcoal finely-powdered 
potassium nitrate. What occurs? 

Common gunpowder is a mechanical mixture of potas- 
sium nitrate, sulphur, and charcoal. Gun-cotton and 
wood-powder are made by treating vegetable fibres with 
nitric acid. 

Exp. 65 p. To about 20 cc pure water in an evaporating dish 
add one or two drops of nitric acid. Now drop in some goose- 
quill clippings or the parings of the finger-nails. Evaporate the 
solution to dryness, when the cuttings will turn yellow. Also 
try the same upon white silk thread. What occurs? 

Query. How does nitric acid act upon the skin and similar organic 
substances ? 

Exp. 66 p. Drop a few drops of nitric acid upon copper 
filings in a test-tube, and note the brownish-red fumes evolved. 
What are these fumes ? 

When metals react with nitric acid, substances called 
nitrates are obtained, some of which are very useful, as we 
shall hereafter see. 

Nitric acid is one of the most important acids known in 
chemistry. In addition to the uses above indicated, we 
may add that it is used in making coal-tar colors and 
various other economical products, while in the laboratory 



70 NITROGEN AND OXYGEN. 

it is used as an indispensable reagent, serving as a solvent 
for most metals, — since the nitrates are all soluble in 
water, — and as a point of departure in the preparation of 
all the other oxides and acids of nitrogen. 

75. Tests for Nitric Acid, HN0 3 , and the Nitrates. — 

1. MaKe in a test-tube a solution of ferrous sulphate, 
FeS0 4 , and add sulphuric acid, H 2 S0 4 . Shake well, and 
allow to stand till cool ; then, without mixing, carefully 
pour in the solution to be tested. Now lightly tap with 
the finger on the side of the test-tube. If nitric acid or a 
nitrate be present, a brown ring will be formed where the 
liquids meet. Upon shaking, the ring disappears. 

Explanation. Nitric oxide, NO, is liberated, which, uniting with the 
ferrous sulphate, forms the brown substance of the ring, thus : — 
2 KN0 3 + 4 H 2 S0 4 + 10 FeS0 4 .- 
K 2 S0 4 + 3Fe 2 (S0 4 ) 3 + 4 H 2 + 2(FeS0 4 ) 2 N0 . 

2. A solution of a nitrate with sulphuric acid and a few 
bits of copper will give off reddish fumes. 

Expl. 2KN0 3 + 4H 2 S0 4 + 3Cu = K 2 S0 4 + 3CuS0 4 + 4H 2 + 2 NO . 
The NO coming in contact with the air absorbs atmospheric oxygen, thus : 
2 NO + 2 O = 2 N0 2 . What is N0 2 ? 

8. Nitrates are distinguished from nitrites thus : Add 
acetic acid to ferrous sulphate, then add the solution to be 
tested. Nitrates produce no change : nitrites turn the 
solution brown. 



Hydroxyl amine, NH3O. 

76. Nitrogen, hydrogen, and oxygen, form another com- 
pound of some scientific interest, hydroxylamine, NH 3 0, 
which may be regarded as a compound of ammonia and 



NITROGEN AND OXYGEN. 71 

oxygen. If we represent ammonia thus, N -j H , we may 

represent hydroxylamine thus, X ] H , showing that the 

(OH 

group OH, or hydroxyU which the student must have 
noticed as occurring in the hydroxides, has displaced one 
atom of hydrogen in ammonia. 

This substance in an aqueous solution possesses strong 
reducing powers, being capable of throwing down, in a 
finely-divided state, some of the metals from their solu- 
tions. It is produced by the action of nascent hydrogen 
on nitric oxide, thus : — 

NO + 3H = NH s O. 

It turns a solution of cupric sulphate orange-yellow, 
forming cuprous oxide, Cu 2 0. This reaction serves as a 
test. 

EXERCISES IN NITROGEN. 

1. Prob. How many litres of air would be required in preparing 5 1 of 
nitrogen ? How much phosphorus ? 

2. Make a cork boat, and place thereon a small quantity of iron filings 
moistened with ammonium chloride ; float the boat on water, and place 
over it a tali glass jar, the mouth of which is to dip under water; note the 
volume of air, and in two or three days again examine. What change has 
occurred in the iron ? What alteration in the volume of air ? How can 
you determine the volume of and X in air, provided the iron has united 
•vith all the oxygen ? Test the residual gas. Is it nitrogen ? 

3. Prob. How many grams of NH 3 can you obtain from 80s of XH 4 Cl? 

4. Prob. How many grams of nitrous oxide are to be had from 400s of 
NH 4 N0 3 ? 

5. Prob. How many pounds of nitric acid may be obtained from one 
ton of Chili saltpetre ? How much H 2 S0 4 will be required to produce it 3 

6. If you had KN0 3 , H 2 S0 4 , Xa, Hg, starch, and NH 4 OH, and no other 
reagents, show how you could prepare all the oxides and acids of nitrogen 
excepting N 2 5 . 



72 NITROGEN AND OXYGEN. 

7c Which compound treated in this chapter is. the most valuable to 
commerce ? Which next ? 

8. Write a short sketch of the chemist Rutherford, who discovered 
nitrogen in 1772. 

9. What is the derivation of the words nitre and nitrogen? (Consult a 
dictionary.) 

10. NH 3 represents tico volumes of ammonia. In its production, one 
volume of N has united with three volumes of H. How much condensa- 
tion has occurred? What is the density (Art. 87) of NH 3 as compared 
with H ? (Sua. 14 + 3 = 17 and 17 -+ 2 = 8.5.) What is the density of 
N 2 ? Of N 2 3 ? 

11. In practice one determines the amount of ammonia present in 
drinking-water, thus ; Proceed as in Exp. 35, using l l of the water to be 
tested. The first jar contains three-fourths of all the ammonia in the 
sample (Wanklyn). In a similar tall jar is placed 50 cc pure water and 
about 4 CC Nessler's solution. To this, from a burette graduated to tenths 
of a cubic centimetre, is added a standard solution of ammonium chloride, 
NH 4 C1, drop by drop, with constant stirring until the same color is reached 
as in the first jar (Exp. 35). The number of cubic centimetres standard 
solution added equals three-fourths of the number of milligrams of ammo- 
nia per litre. 

The standard solution of ammonium chloride is prepared by dissolving 
3.15? of the dry salt in l 1 distilled water. See App., Art. 78. 

Good drinking-water should not contain over 0.08 parts per 1,000,000, 
of free ammonia. 

Query. Should the qualitative tests fail to detect organic matter, 
ammonia, nitrites, etc., can there be a question as to the potableness of 
the water under examination 1 

12. Nitric acid containing oxides of nitrogen may be freed from the 
latter by passing through it for some time a current of pure air. 

General Note. Recent investigations throw doubt upon the existence 
of free nitrogen trioxide in a gaseous condition. Some authors also give 
ammonium hydroxide, NH^OH ; but there are grave doubts as to its exist- 
ence. It is, at least, decomposed by boiling. 



CHAPTER IV. 

BINARY COMPOUNDS. — ACIDS. — BASES. — SALTS. — 
CHEMICAL NOMENCLATURE. 

77. Binary Compounds are those which consist of but 
two elements. Oxygen unites with all other elements 
except fluorine, and the compounds thus formed are known 
as oxides. Similarly, the binary compounds of sulphur are 
known as sulphides ; those of chlorine, bromine, and iodine, 
as chlorides, bromides, and iodides. 

The principal elements whose binary compounds are 
named in this way are bromine, chlorine, fluorine, iodine, 
oxygen, selenium, sulphur, and tellurium. 

To distinguish between the different oxides, chlorides, 
etc., the name of the element in combination with oxy-gen, 
chlorine, etc., is prefixed. Thus sodium chloride is the 
compound of sodium and chlorine ; magnesium chloride is 
the compound of magnesium and chlorine; barium oxide 
is the compound of barium and oxygen ; potassium iodide, 
the compound of potassium and iodine, etc. 

Sug. Student, name the compounds, the formulae of which are here 
given:— Ca( ^ BaC1 ^ KF ^ -^ MgQ 

It sometimes occurs that oxygen, chlorine, bromine, etc.. 
unite with other elements in more than one proportion, as 
illustrated by the formulae, HgO and Hg 2 0, CuO and 
Cu 2 0, FeCL and Fe Cl s , etc. In these cases the simple 
prefixing of the name of the element which is in combina- 
tion with oxygen, chlorine, etc., will not suffice. Hence 



74 BINARY COMPOUNDS. 

the name is modified by the suffixes -ic and -ous. We 
have not simply mercury compounds, but mercuric and 
mercurous compounds, etc. That compound which con- 
tains the smaller proportion of oxygen, chlorine, etc., is 
designated by the suffix -ous, and that which contains 
the larger proportion is designated by the suffix -ic. 
Thus, of the two compounds of mercury and oxygen, that 
which has the formula Hg 2 is called mercurous oxide, 
because it contains less oxygen in proportion to the mer 
cary than the other compound, HgO. The latter is called 
mercuric oxide. In naming compounds of copper, iron, tin, 
lead, and some other elements, when the syllables -ic 
and -ous are necessary, the Latin names of the elements 
are used. Instead of speaking of copperous and copperic, 
or of ironous and ironic compounds, we use the words 
cuprous and cupric, ferrous and ferric, compounds, etc. 
The compounds CuO and Cu 2 are known respectively as 
cupric and cuprous oxides : FeCl 2 and Fe Cl 8 are called 
ferrous and ferric chlorides. 

There are cases in which a given element unites with 
oxygen, chlorine, etc., in more than two proportions. It 
is then necessary to use other methods in naming the com- 
pounds. Manganese forms four compounds with oxygen. 
These have respectively the compositions expressed by the 
formulas MnO, Mn 2 3 , Mn 3 (X, and Mn0 2 . To these are 
sometimes given the names manganous oxide, MnO ; man- 
ganic oxide, Mn 2 3 ; manganoso-manganic oxide, Mn 3 4 , 
the name signifying that the compound is made up of 
manganous and manganic oxides ; and manganese dioxide, 
Mn0 2 . 

It is not uncommon to indicate by the name the numbej 
of oxygen atoms represented in the formula, as in the 
case of oxides. 



ACIDS. 75 

Those containing one atom of oxygen are called monoxides; 
" two atoms u " dioxides; 

" ^7i?-ee ,; " " trioxides; 

" /ow " " Ct tetr oxides ; 

" j^re " " " pentoxides, etc 

The relation 2 to 3 is sometimes expressed by the word 
" sesqui," e.g., Fe 2 3 , sesquioxide of iron, which is the old 
name for what is now called ferric oxide. 

78. Acids. — Among the compounds thus far considered 
are nitric and nitrous acids ; and frequent reference has 
been made to sulphuric acid and hydrochloric acid. Indeed, 
it would be difficult to write a page on any chemical sub- 
ject without the use of the word "acid." What is an 
acid? An exact definition cannot well be given. By the 
term " acid " we mean a body with certain physical and 
chemical properties, the chief of which are the following : 
a sour taste ; the power to turn certain vegetable colors, 
as to turn blue litmus red ; the power of giving up hydro- 
gen, and taking up metals (bases) in its place. 

Exp. 67 p. Student, test with blue litmus every acid to be 
found in the laboratory. Do all the acids have the same effect 
on the color? In testing, take a few drops of the acid in a 
test-tube half full of water. Try substances which are not 
acids, as common salt. What effect is produced? 

According to the above statement regarding the proper- 
ties of acids, all acids must contain hydrogen. It does not 
follow that all bodies which contain hydrogen are acids. 
Ammonia, NH 3 , for example, has properties quite the 
opposite of those possessed by acids ; and many other 
examples might be cited. In order to have acid proper- 
ties, we must have the hydrogen in combination with cer- 
tain elements, or groups of elements. 



76 ACIDS. 

The elements whose hydrogen compounds are markedly 
acid are chlorine, bromine, iodine, and fluorine, which give 
hydrochloric acid, HC1 ; hydrobromic acid, HBr ; hydriodic 
acid, HI ; and hydrofluoric acid, HF. The hydrogen com- 
pounds of sulphur, selenium, and tellurium, are weak acids. 

Most acids consist of hydrogen in combination with 
oxygen and some other element, as nitric acid, HN0 3 ; 
nitrous acid, HN0 2 ; sulphuric acid, H 2 S0 4 , etc. They 
are commonly called oxygen acids to distinguish them from 
those which contain no oxygen. There are a great many 
acids belonging to this class, but only a few of them are 
in common use. 

In naming the oxygen acids, the same suffixes -ous and 
4c are used, as in the case of binary compounds, and 
with the same significance. 

If an element forms only one acid with oxygen and 
hydrogen, the suffix -ic is used. If it forms two acids, 
that which contains the smaller proportion of oxygen is 
designated by the suffix -ous, and that which contains 
the larger proportion of oxygen, by the suffix -ic. Thus 

we have 

Nitrous acid, HN0 2 , 
and Nitric acid, HN0 3 ; 

Sulphurous acid, H 2 S0 3 , 
and Sulphuric acid, H 2 S0 4 , etc. 

In those cases in which more than two acids are formed 
by the same elements, prefixes are used in addition to the 
suffixes. A good illustration of the use of these prefixes is 
furnished by the acids of chlorine. This element forms 
four acids with oxygen and hydrogen. They are repre- 
sented by the formulae HCIO, HC10 2 , HC10 3 , and HC10 4 . 
Of these the second and third are known as chlorous and 



BASES AND SALTS. 77 

chloric acids. The first is called hypochlorous acid, which 
signifies that it is below chlorous acid as regards the 
amount of oxygen it contains. The fourth is called per- 
chloric acid, which signifies that it is beyond chloric acid 
in the series. These prefixes hypo- and per- are frequently 
used in this sense. 

79. Bases. — There are certain compounds which have 
properties almost exactly the opposite of those of acids. 
They are called bases. The name "base" has been applied to 
various bodies, and with different meanings. In general, we 
mean by a base a substance which has the power of neutral- 
izing acids, that is, destroying their acid properties. The 
bases, like the acids, consist of certain elements in combi- 
nation with oxygen and hydrogen. Some elements unite 
with oxygen and hydrogen to form acids ; and others 
unite with oxygen and hydrogen to form bases. Nearly 
all the compounds which the metals form with hydrogen 
and oxygen are bases. Examples are : potassium hydrox- 
ide, KOH ; calcium hydroxide, Ca(OH) 2 , etc. The stronger 
bases are known as alkalies, among which are the hydrox- 
ides of potassium and sodium, formerly called caustic potash 
and caustic soda. 

80. .Salts. — When an acid and a base react, they tend 
to neutralize each other. The acid properties and the 
basic properties are usually both destroyed, and a new 
body is formed which is neither acid nor base. This new 
body is called a salt. The relation between an acid and 
the salts derived from it will readily be seen by examining 
the following formulae : — 

rNaCl, 
Hydrochloric acid, HC1, yields the salts 1 KC1, 

L CaCl,, etc, 



78 SALTS. 

rKN0 3 , 

Nitric acid, HN0 3 , yields the salts . 1 NaN0 3 , 

tBa(N0 8 ) 2 , etc. 

!K 2 S0 4 , 
BaS0 4 , 
Na 2 S0 4 , etc. 

On comparing the salts with the acid from which they 
are derived, we see that the difference between them is 
simply this, that the acid contains hydrogen while the 
salts contain something in the place of the hydrogen. 
We shall see later that this something which takes the 
place of hydrogen is called a metal. Thus, in the exam- 
ples given above, the metals sodium, Na, potassium, K, 
calcium, Ca, and barium, Ba, take the place of hydrogen 
in the acids. 

Each acid can yield at least one salt with every metal, 
and in some cases more than one. The salts of each acid 
receive a general name, and we distinguish between the 
different salts of the same acid by prefixing the name of 
the metal. 

The salts of the simplest acids, such as hydrochloric, 
hydrobromic, and hydriodic acids, are named, as described 
above, under the head " Binary Compounds" (see p. 73). 

Salts of the oxygen acids are named thus : when the 
name of the acid ends in ic, the name of its salts ends in 
ate ; and, when the name of the acid ends in ous, the name 
of its salts ends in ite. Thus, a salt of nitric acid is called 
a nitrate ; of nitrous acid, a nitrite ; of sulphuric acid, a 
sulphate ; of sulphurous acid, a sulphite, etc. From nitric 
acid we thus have a series of nitrates corresponding to 
the different metals. We distinguish between them by 
using the names of the metals as adjectives, as in the case 
of binary compounds. The potassium, sodium, and cal- 



SALTS. 79 

cium salts of nitric acid, for example, are called potassium 
nitrate, KN0 3 , sodium nitrate, NaN0 3 , and calcium nitrate, 
Ca(N0 3 ) 2 . 

The metals mercury, iron, copper, and some others yield 
two different classes of salts, corresponding to the lower 
and higher oxides already mentioned. Just as we have 
mercurous and mercuric oxides and chlorides, ferrous and 
ferric chlorides, etc., so also we have mercurous and mer- 
curic nitrates, sulphates, etc., and ferrous and ferric ni- 
trates, sulphates, etc. The two nitrates of mercury will 
serve as examples. We have 

Mercurous nitrate, Hg!TO 3 , 
and Mercuric nitrate, Hg(N0 3 ) 2 . 

The principle of nomenclature adopted for these salts is 
the same as that described in connection with the oxides, 
chlorides, etc. The name of that salt which contains the 
smaller proportion of the acid constituent ends in ous* 
while the name of that one which contains the larger pro- 
portion of the acid constituent ends in ic. 

The action of metals upon acids may be illustrated by 
the following equations : — 

Zn + H 2 S0 4 = ZnS0 4 + 2 H ; 
Zn + 2HC1 =ZnCl 2 +2H. 

In these cases the metal simply replaces the hydrogen 
which is set free. This action takes place only in the case 
of the stronger acids. 

When an acid acts upon a base, the action is as repre< 
sented below : — 

KOH + HN0 3 = KN0 3 + H 2 0; 

NaOH + HN0 3 = NaN0 3 + H 2 ; 

2 KOH + H 2 S0 4 = K 2 S0 4 + 2 H 2 ; 

Ca(OH) 2 + H 2 S0 4 = CaS0 4 +2H 2 0. 



80 ACID AND NORMAL SALTS. 

This kind of action takes place between all acids and 

all bases. 

81. Acid and Normal Salts. — The simplest acids, such 
as hydrochloric and nitric acids, yield only one salt each 
with most of the metals. Thus hydrochloric acid and 
potassium yield only one potassium chloride, KC1, which 
is a neutral body; nitric acid and sodium yield only one 
sodium nitrate, NaN0 3 , which is also neutral. 

There are some acids, like sulphuric acid, H 2 S0 4 , which 
have the power of yielding two or more salts with the 
same metal. Thus sulphuric acid yields with potassium 
not only the salt, K 2 S0 4 , potassium sulphate, but another 
salt, of the formula KHS0 4 , which contains only half as 
much potassium as the first. In the first case all the 
hydrogen of the acid has been replaced, and the resulting 
compound has no acid properties. It is a normal salt. In 
the second case a part of the hydrogen is left, and the 
compound still has acid properties. It is both acid and 
salt, and is called an acid salt. 

A normal salt is one which is formed by replacing all 
the hydrogen of an acid with a metal. 

An acid salt is one which is formed by replacing only a 
part of the hydrogen of an acid with a metal. 

In naming the acid salts it is customary to indicate the 
number of atoms of the metal which are represented in 
the formula. Thus the salt KHS0 4 is called mono-potas- 
sium sulphate ; the salt Na 2 HP0 4 is called disodium phos- 
phate. Sometimes they are referred to as acid salts, 
mono-potassium sulphate being called acid potassium sul- 
phate. 

Applications of these principles of nomenclature will be 
met with when the salts are considered. Meanwhile the 



ACID AND NOKMAL SALTS. 81 

student should familiarize himself with the main points 
by means of examples furnished by the teacher. A few 
examples are here given. 

Student, name the compounds, the formulae of which 
are given below : — 

Cu 2 Cl 2 , KN0 3 , Ca(N0 3 ) 2 , Fe(N0 3 ) 2 , HgO, NaHSO,, 
CuCl 2 , NaN0 2 , Ba(N0 3 ) 2 , Fe (N0 3 ) 3 , Hg 2 0, K 2 SO,. 

WRITING EQUATIONS. 

It is important to know how to write chemical equations, and thus avoid 
the necessity of committing them to memory. In the first place we know 
what substances we put together or experiment upon, and these are placed 
in the first member, and connected by the sign +. The substances formed 
are determined by experiment, or, when our knowledge is sufficient, by 
analogy or by induction. They are then placed in the second member, 
and connected by the + sign. It now remains to balance the equation. 
The fundamental principle to be remembered here is, that " matter is in- 
destructible " ; that is, just as many atoms of a given element as appear in one 
member, just so many must also appear in the other. Let us, for example, 
write the equations for the reaction of NaCl and H 2 S0 4 : we first write 
NaCl + H 2 S0 4 = •••; by experiment, we know that under certain conditions 
(Art. 94) HC1 and HNaS0 4 are formed, and we proceed to the next step, 
thus : NaCl + H 2 S0 4 = HNaS0 4 + HC1. By inspection, we see that the 
equation balances and is complete. But let us suppose that the conditions 
are different, and that Na 2 S0 4 and HC1 are produced ; the second step 
gives us NaCl -f H 2 S0 4 = Na 2 S0 4 + HC1. By inspection we here see that 
the equation is not true, since two atoms of Na appear in the second mem- 
ber, and but one in the first ; also one atom of H in the second, and two 
in the first. We may obtain the required amount of Na by doubling the 
NaCl ; and, when this is done, the necessity for doubling the HC1 becomes 
apparent, and the equation balances, thus : — 

2 NaCl + H 2 SO, = Na 2 S0 4 + 2 HC1. 

Water, which is almost always present, must sometimes be taken 
into consideration. The equations previously given will afford good prac- 
tice, also those to follow, especially those relating to the metals. Before 
we reach that point, however, molecular equations will be explained. 



CHAPTER V. 

THE ATMOSPHERE. LAWS OF PRESSURE, TEMPERATURE, 

DENSITY, AND VOLUMES OF GASES. PROBLEMS. 

THE ATMOSPHERE. 



82. The earth is everywhere surrounded by an ocean of 
gaseous vapor, called the atmosphere, which varies from 
fifty to one hundred miles in height. This variation at 
any one point is never ceasing, for just as in the oceans of 
water, so in this ocean of air, do huge waves continually 
surge to and fro, — -waves so vast that their altitudes are 
measured in miles. 

Eveiy object upon the surface of the earth is subjected 
to the pressure exerted by the weight of air above. This 
pressure varies constantly, and, owing to the great mobility 
of the particles of air, it is exerted in all 
directions, — downwards, upwards, and side- 
wise. 

This pressure is measured by an instru- 
ment called a barometer (Fig. 15). A is a 
glass tube about 800 mm long, sealed at the 
upper end, open at the lower, and provided 
with a scale. This tube is filled with mer- 
cury, and inverted in a cup of mercury, 
C. Now, since the tube itself sustains 
the pressure which the atmosphere would 
Fig. 15. exert on this column of mercury within the 




THE ATMOSPHERE. 



83 



tube, in every direction except upwards, it follows that 
the column will remain at a higher altitude than the level 
of the mercury in the cup. The height of this column 
of mercury will depend upon how hard the atmosphere 
presses it upward. 

At the level of the sea, in the latitude of Paris, and at 
0° C, the average height of this column is 760 mm ; hence 
760 mm is taken as the standard pressure of the air. 

As you ascend from the sea-level the column falls 
(why?), and as you descend it rises (why?). 

As the density (Art. 88) of the mercury and the at- 
mosphere varies, owing to changes of temperature, the 
height of the barometer varies ; hence the necessity of 
taking a standard temperature, which is 0° C. 



/Off: 



83. Measurement of the Temperature of the Atmos- 
phere. — This is accomplished by means of instruments 
called thermometers. There are three scales in use, — 
Centigrade, Fahrenheit, and Reau- 
mur (Fig. 16). Thermometers are 
made by blowing bulbs on capillary 
tubes. The bulbs and tubes are filled 
with mercury, and then heated till 
the mercury issues in vapor, when 
the ends are suddenly sealed by the 
blow-pipe flame. They are graduated 
by first plunging them into melting 
ice, the height of the column of mer- 
cury being marked 0° C, 0° R., or 
32° F. The instruments are next 
placed in the steam of boiling water, 
and the height of the column of mercury marked 100° C, 
80° R., or 212° F, The distances between these points are 



Fig. 16. 



84 THE ATMOSPHERE. 

then divided into spaces (or degrees), there being 100 
divisions C, 80 R., or 180 F. ; divisions of the same length 
are also made above and below these points. From the 
manner of laying off these scales, it follows that 
5° C. = 4° R. = 9° F. 

The following formulae will assist in changing from the 
reading of one scale to another : — 

(a)C. = (F.-32)f 

(6) F. =f C. +32. 
(c) R. = *C. 
Prob. Change 98° C. to F. ; 87° R. to F. ; 91° F. to R. ; 
-18°C. toF. ; -40°F. to C. 

Sug. It would be advisable for the student to learn the points of a 
good thermometer from his text-book in physics, and to review the metric 
system in his arithmetic. 

Note. The centigrade thermometer and the metric system of weights 
and measurements are used throughout this work, as they best answer its 
purposes, and are the ones used by scientists in general. 

84. Impurities in the Atmosphere. — As we have 
already learned, air is a mechanical mixture of nitrogen 
and oxygen. By this we mean pure air. But atmos- 
pheric air is never pure. It contains, — 

(a) Moisture, as invisible vapors, clouds, and fogs. 
These, being lighter than the atmosphere, cause a lower 
barometer, especially when they are present in large 
quantities. 

(&) Carbon dioxide, C0 2 , produced by combustion, by 
the respiration of all air-breathing animals, and by the 
decomposition of animal and vegetable tissues. 

(<?) Ammonia (Art. 51), and Argon, etc. (p. 33). 

(c?) Ozone (Art. 30), or other substances having marked 
oxidizing power. 



THE ATMOSPHERE. 85 

(e) Dust and smoke. 

(/) Other gases in small quantities, which are liberated 
in various ways. 

85. Determination of the Volumes of Nitrogen and 
Oxygen in the Atmosphere. — This determination is 
made by means of Ure's eudiometer. A measured quan- 
tity of pure air is introduced into the graduated limb, 
and then a volume of hydrogen, more than sufficient to 
combine with the oxygen of the air, is added. The whole 
volume is now carefully noted, the spark passed, and the 
diminution of volume carefully ascertained. 

One-third of this diminution equals the volume of the 
oxygen contained in the air. 

The volume of oxygen is subtracted from the volume of 
air introduced at the beginning, and this gives the volume 
of the nitrogen. 

In this way we learn that the air consists of oxygen 21 
volumes, and nitrogen 79 volumes, in 100 parts. These 
proportions vary but slightly in any locality or season. 

Queries. What chemical action takes place when the spark is passed ? 
How do you know one-third of the volume of diminution to be the volume 
of % Through what substances would you pass air to remove its im- 
purities ? 

86. Effect of Pressure on the Volume of a Gas. — If 

a mass of gas be confined in an air-tight cylinder, and a 
perfectly-fitted piston be pressed down into the cylinder, 
the gas will be compressed into a smaller volume. 

The law for the volume of a gas under such conditions 
is: — 

Law I. The volume of any gas, its temperature remaining 
constant, varies inversely as the pressure. 



86 THE ATMOSPHERE. 

We mean by this that volume 1 under pressure 1 
becomes volume J under pressure 2, volume J under 
pressure 3, or volume | under pressure 4, etc. ; and the 
reverse of this is also true when the temperature remains 
the same in both cases. (How could this law be discov- 
ered if it were unknown ?) 

Note. On lQ cm , at the standard pressure of 760 mm , the atmosphere 
exerts a pressure of 1033.3s (nearly 15 lbs. per sq. in.), which is called a 
pressure of 1 atmosphere. A pressure of 2 atmospheres is 2 X 1033.3s, etc. 
Now, since gases are subject to the pressure of the atmosphere, their 
volume varies with every change of the barometer. 

Sug. The student should consult some work on physics for the expert 
mental demonstration of the above law, as well as for that of the succeed- 
ing law, since we use them as an application of physics to chemistry. 

Problems. 1. What volume will 10 1 of gas at 762 mm occupy- 
when the barometer stands at 758 mm ? 

Solution. Since the volume varies inversely as the pressure, we have 
the proportion, 

758 : 762 : : 10 : x = 10.0527 + litres. Ans. 

2.' 190 cc of gas at 760 mm pressure becomes how many cubic 
centimetres at 765 mm ? 

3. A mass of gas, 100 1 under 755 mm , is subjected to a 
pressure of 4.5 atmospheres; what volume will it occupy? 
Ans. 22.076+ litres. 

Note. In these problems the temperature is considered constant. 

87. Effect of Heat on the Volume of Gases. — It has 

been found by experiment that 273 volumes of any gas 
at 0° become 274 volumes when its temperature is raised 1°, 
275 when raised 2°, etc., increasing one volume for each 
degree of increase in its temperature ; also that 273 volumes 
at 0° become 272 volumes when its temperature is lowered 
1°, 271 volumes when lowered 2°, 270 when lowered 3°, 



THE ATMOSPHERE. 87 

etc., decreasing one volume for each degree of decrease in 
its temperature. According to this, the volume of a gas at 
— 273° C. would be ; and this point is designated as the 
absolute of temperature. Hence the absolute tempera- 
ture of any body is the temperature above the ordinary 
+ 273, or t + 273. Taking these ideas into account, we 
have : — 

Law II. The volume of any gas, its pressure remaining con- 
stant, varies as its absolute temperature, i.e, in the ratio of 
273 + t to 273 + V. 

Rem. 1. ^ is the observed temperature of the gas, and t' the required 
temperature. 

Rem. 2. Since any gas surrounded by the atmosphere will usually be 
of the same temperature as the atmosphere itself, it follows that the 
volume of that gas will vary as the thermometer varies. 

Problems. 1. At + 15° the volume of a gas is 84 1 ; what 
will be its volume at + 85° ? 

Solution. 273 + 15 : 273 + 85 : : 84 : x = 104.4166 + litres. Ans. 

2. A gas at —15° has a volume of 18 1 ; what will be its 
volume at 100°? 

Solution. 273 - 15 : 273 + 100 : : 18 : x = 26^ litres. Ans. 

3. 98 1 of gas at — 4° become how many at — 24°? 

4. 176 1 of gas at + 100° become how many at — 140°? 

5. 80 1 of gas at 0° become how many at — 18°? 

6. 144 1 of gas at — 15° become how many at 0°? 

Note. In these problems the pressure is considered constant. 

Problems in which both pressure and temperature vary : — 
1. A mass of gas at + 15° and 762 mm pressure occupies 94 1 ; 
what will be its volume at + 25° and 758 mm pressure ? 

Solution. We here have a combination of the principles of Arts. 86 
and 87, pressure and temperature both affecting the volume of the 94 1 in 



88 THE ATMOSPHERE. 

question. We will consider them separately ; hence the compound pro- 
portion : — 

| (1) Temperature, 273 +15 : 273 + 25 | ; ; M ; x = „ ^ ^ 
I (2) Pressure . . . 758 : 762 J 

2. 90 cc of gas at 0° and 760 mm occupy what volume at - 140° 

and 40 atmospheres? Ans. 1.09 + -cubic centimetre. 

Note. From this the student may judge of the effect of pressure and 
reduction of temperature. 

3. 72 1 at —12° and 4 atmospheres pressure become how 
many litres at 100° and 760 mm ? 

4. What volume will any quantity of a gas occupy at 
— 273° C. ? In cooling any gas from ordinary temperatures 
down toward absolute zero, a point is reached where the gas 
becomes a liquid, even under ordinary pressure. This point is 
called the critical temperature. If the temperature is kept 
constant and the pressure sufficiently increased, the gas also 
becomes a liquid at the critical pressure for that temperature. 

Liquid Air. — Air is now liquefied by allowing cooled, 
compressed air to expand in a vertical non-conducting cylin- 
der. The rapid expansion of the compressed air soon re- 
duces a portion of it below its critical temperature, which 
immediately causes that portion to assume a liquid form. 

Liquid air is now useful in producing extremely low 
temperatures for scientific research. Many industrial uses 
have been proposed, also, but none have proven practical. 

88. Relation of Weight to Density. — By the density 
of a substance we mean the amount of that substance 
contained in a given volume. We have seen how the 
volume of a gas varies under differences of pressure and 
of temperature. Now, it is evident that its density varies 
also ; i.e., whatever tends to make the volume less makes 
the density greater, and whatever tends to make the vol- 



THE ATMOSPHERE. 89 

ume greater makes the density less. Again : it is evident 
that the denser a given amount of gas, the greater will be 
its weight, and the less dense the gas, the less its weight; 
or, — 

The weight of a given volume of gas values directly as its 
density. 

Problems. 1. How much will 10 1 of oxygen weigh at +15° 
and 765 mm ? 

Solution. We know that l 1 of oxygen at 0° and 760 mm weighs 1.430s ; 
therefore we will find how many litres this gas will be at 0° and 760 mm , as 
in Art. 87, and then multiply that result by 1.430, thus : — 

I 288 : 273 X : : 10 : x = 9.54151 ; and 9.5415 X 1.430 = 13.644s. Arts. 
\ 760 : 765 J 

2. How much will 20 1 of hydrogen weigh at 755 mm and +20°? 

3. How much will 15 1 of nitrogen weigh at —112° and 29 
atmospheres pressure ? 

89. Useful Problems. — I. To find the percentage com- 
position of a compound. We will explain this by solving 
a problem : What per cent of N and H in NH 3 ? 

Solution. ^ow, it is evident that T 3 T of NH 3 is hydrogen, and \i 

N = 14 is nitrogen. T 3 7 expressed in the form of per cent equals 

3H = 3 300 h- 17 = 17.65 % of H. One can also readily understand 

NH 3 = 17 that 10 ° % ~ 17 - 65 % = 82 - 35 % of N - 

These percentages are valuable in that they enable us 
to make computations more rapidly. For example, if we 
wish to know how much hydrogen there is in 10 g of am- 
monia, we have simply to multiply 10 g by the per cent of 
hydrogen, and divide the result by 100, when we have the 
weight of the hydrogen in grams, thus : — 
(17.65 x 10) --100 = 1.765*. 

1 . What per cent of oxygen in HgO ? KC10 3 ? 

2. What per cent of chlorine in NaCl? Of sodium? 



90 THE ATMOSPHERE. 

II. To find what volume will be occupied by a gas 
obtained from a certain weight of chemicals. We can 
also best understand this by a problem : How many litres 
of oxygen can be obtained from 10 g of potassium chlorate, 
KCIO3, when the barometer reads 750 mm and the thermom- 
eter 25°? 

Solution. We will first ascertain what weight of oxygen 10s of KC10 3 
will yield. We can best do this by multiplying 10 by the per cent of in 
KCIO3. Thus we find the weight of oxygen to be 3.918s. We will now 
ascertain how many litres 3.918& of oxygen will occupy at 760 mm and 
0\ One litre of oxygen under these conditions weighs 1.430s ; hence, 
3.918 *■ 1.430 = 2.7398 1 , or the number of litres at 0° and 760 mm . We 
can now finish the problem by Arts. 86 and 87, thus : — 

f 750: 760 1 .. 2 .7398 :* = 3.0800. 

1273: 298 J 

1. How many litres of oxygen gas may be had from 100 s 
HgO when the barometer stands at 755 rara , the thermometer 
reading 20° ? 

Sua. HgO (heated) = Hg + O. 

2. How m'any litres of oxygen gas may be had from 500 g 
Mn0 2 , at 20° and 4 atmospheres pressure? 

Sug. 3 MnO, (heated) = Mn 3 4 +20. 

3. How many litres of nitrous oxide may be obtained from 
l k of NH4NO0 when the barometer reads 750 mm and the ther- 
mometer + 22°? 

Sug. See Nitrogen Monoxide. 

III. To find the iveight of chemicals required to yield a 
certain volume' of gas. Let us again have recourse to a 
problem: How many grams of KC10 3 will be required to 
fill with oxygen a receiver of 32 1 capacity at 20° and 

750 mm ? 



THE ATMOSPHERE. 91 

Solution. We will first find what volume 32 1 of oxygen at 20° and 
750 uun would become when reduced to 0"* and 760 nun , in order to find the 
required weight of the oxygen, thus : — 



I 760 : 750 i 



29.4231. 



Now, 29.423 X 1.430 = 42.074s, or the required weight of oxygen. We 
may now obtain the desired weight of the potassium chlorate by dividing 
the weight of the oxygen by the percentage of O in KC10 3 , or by the 
proportion: 48 : 42.074 :: 122.5 : *. 

1. How many grams KC10 3 will be required to yield 20 1 of 
oxygen at - 20° and 760 mm ? 

2. How many grams of zinc and sulphuric acid are needed to 
yield 40 1 of hydrogen at + 24° and ,d5 mm ? 

Sug. Zn + H.SO^ = ZnS0 4 + 2H. 

3. What weights of CaO and NH 4 C1 are required to make 
25 1 of NH 3 at 15° and 749 mm ? 

Sug. CaO + 2 NH 4 C1 = CaCl 2 + H 2 + 2 NH 3 . 



EXERCISES. 

1. The following equations may be of service in making calculations 
upon gases : — 

VH VB> 



273 + * 273 + *' 

V 9 H, and t represent respectively the volume, height of barometer, and 
temperature of a gas under observed conditions, while V, H r , and V rep- 
resent the same under required conditions, one of which will be unknown. 
When t = t 1 we have, 

(2) VH= V'H' (Art. 86). 

VVlien H — H' we have, 

V V 

(3) — : — = — (Art. 87). 

y } 273 + t 273 + t' } 

2. Make a table showing the relations between the acids and their salts 



CHAPTER VI. 

CHLORINE. — ITS OCCURRENCE, ETC. — HYDROCHLORIC 

ACID. — AQUA REGIA. — CHLORINE OXIDES. — CHLO 

RINE OXACIDS. 

CHLORINE. 

Symbol Cl'. — Atomic Weight, 35.5; Specific 
Gravity, 2.450. 

90. Occurrence. — Chlorine does not occur free in 
nature, owing to its great chemical activity ; in combi- 
nation with certain metals, however, it occurs in large 
quantities, as in sodium chloride, NaCl, or common salt. 
Silver chloride, AgCl, potassium chloride, KC1, calcium 
chloride, CaCl 2 , and magnesium chloride, MgCl 2 , occur in 
smaller quantities. 

91. Preparation. — Exp. 68 p. In a test-tube place a 
small quantity of manganese dioxide, Mn0 2 , and add hydro- 
chloric acid, HC1. Upon gently warming, chlorine is evolved 
as a heavy, yellowish, suffocating gas, thus : — 

Mn0 2 + 4 HC1 = MnCl 2 + 2 H 2 + 2 Cl. 

Hold in the escaping gas strips of moistened litmus paper and 
calico printed in organic colors; they will be bleached. Also 
note the fumes. 

This method is sometimes employed in making chlorine 
gas for the manufacture of bleaching-powder. (Art. 349.) 

Exp. 69 p. Drop three or four small crystals of potassium 
chlorate into a test-tube, and add hydrochloric acid. Warm 



CHLOK1NE. 93 

gently, and, when the chlorine f nines begin freely to appear, 
immediately add 3 cm or 4 cm of cold water. What occurs may 
be indicated thus : — 

4 HC1 + 2 KC10 3 = 2 KC1 + 2 H 2 + C1 2 4 + 2 CI. 

Try the effect of this solution upon vegetable colors as before 
Also add a few drops of the solution to tinctures of litmus s 
carmine, and indigo ; they will be bleached. 

The above method is one often employed by th& 
chemist in preparing chlorine water for such purposes as 
testing iodine and bromine. Hereafter the student will 
find frequent use for chlorine water thus prepared. It 
might be well to say that the CL0 4 and KC1 are in no 
wise detrimental to the solution. 

Another method of preparing chlorine in the manufac- 
ture of bleaching-powder is of interest, since it is con- 
tinuous and quite inexpensive. Hydrochloric acid gas, 
mixed with air, is passed over heated cupric sulphate, 
CuS0 4 ; the cupric sulphate undergoes no change, while 
the oxygen of the air and the hydrochloric acid react, 

thus : — 

2HC1 + = H 2 + 2C1. 

Another and common method of preparing chlorine is 
as follows : — 

Exp. 70 t. In the generating-flask A (Fig. 17) place equal 
weight of common salt, NaCl, and manganese dioxide, Mn0 2 , 
which have been thoroughly pulverized and mixed. Then add 
to this mixture twice its weight of dilute sulphuric acid (con- 
sisting of equal weights of water and acid) . Apply a gentle 
heat, and chlorine gas is plentifully given off. The Woulff 
bottle B (Fig. 17) contains a little warm water to absorb any 
hydrochloric acid gas that may be produced, while C contains 
strong sulphuric acid to dry the gas. The thistle-top tube con- 



94 



CHLORINE. 



tains a little sulphuric acid. Collect the chlorine in tall jars. 
This may be accomplished by delivering the gas by means of 
a long glass tube extending to the bottom of the upright jar. 
The air will be pushed up and out of the jar. 

Note. This method of collecting a gas is called displacement, and is 
employed with those gases heavier than air. 

If a pure, aqueous solution of chlorine be desired, it 
may be obtained by attaching two or three Woulff 

bottles, nearly rilled with 
cold water, and surrounded 
with a cooling or freezing 
mixture. Should the tem- 
perature of any bottle con- 
tained in the series nearly 
reach 0°, a crystalline hy- 
drate of chlorine is formed, 
whose composition is 
CI + 5 H 2 0. In thus pre- 
paring chlorine we may rep- 
resent the reaction by, — 

2 NaCl + Mn0 2 + 3 H 2 S0 4 = 2 NaHS0 4 + MnS0 4 + 2 H 2 + 2 CI. 

In reality, however, two distinct processes are involved. 
In the first place the sulphuric acid, H 2 S0 4 , acts upon the 
sodium chloride, NaCl, giving hydrochloric acid, HC1, and 
mono-sodium sulphate, NaHS0 4 . Then the manganese 
dioxide, Mn0 2 , acts upon the hydrochloric acid, HC1. 
giving manganous chloride, MnCl 2 , free chlorine, and 
water, H 2 0. If an excess of sulphuric acid is present, it 
decomposes the manganous chloride, MnCl 2 , giving man- 
ganous sulphate, MnS0 4 , and hydrochloric acid ; and 
the latter again acts upon manganese dioxide, yielding 
chlorine. 




CHLORINE. 95 

The equations which give the best insight into the 
reactions are the following : — 

2 NaGl + H 2 S0 4 = Na 2 S0 4 + 2 HC1, 
and 4 HC1 + Mn0 2 = MnCl 2 + 2 H 2 + 2 CI. 

Manganese dioxide readily gives up one part of its oxygen, 

and it is this which, uniting with the hydrogen of hydro 

chloric acid, sets the chlorine free. 

Queries. Why can you not collect chlorine over water or mercury ? 
How can you collect hydrogen by displacement ? 

92. Properties. — Chlorine is a heavy, greenish-yellow 
gas having a strong and suffocating odor, and producing 
great irritation to the lining membranes of the throat 
and nostrils; and, when inhaled in sufficient quantities, it 
is capable even of producing suffocation and death. 

Exp. 71 p. Write with an organic (carmine) ink upon a 
slip of printed paper ; moisten, and hold it in a large test-tube 
full of chlorine gas. The writing disappears and the printing 
remains. Printer's ink is made of lampblack (carbon), and is 
not bleached. 

Queries. How can you distinguish between organic and mineral 
colors ? Try wall paper. Would chlorine water answer as well ? 

Chlorine in the presence of moisture is an invaluable 

bleaching reagent, acting upon vegetable coloring-matters 

thus : — 

2Cl + H 2 = 2HCl + 0. 

^ow this oxygen (liberated, as it is, within the fibres of 
the substance to be bleached), while in a nascent condi- 
tion, seizes upon the coloring-matters, and destroys them, 
or changes them into colorless compounds. 

Exp. 72 t. Saturate with hot turpentine, C 10 H 16 , a strip of 
blotting-paper, and plunge it into a jar of dry chlorine gas- 



96 CHLORINE. 

The turpentine takes fire, the chlorine and hydrogen uniting, 
while carbon is deposited as soot. 

Sug. Student, write the equation. 

Exp. 73 p. Plunge a lighted taper into a large test-tube of 
chlorine. It continues to burn with a dull, red, smoky flame, 
the chlorine again uniting with the hydrogen contained in the 
substance of which the taper is composed, while the carbon is 
set free. 

Rem. Oils, resins, gums, waxes, tallows, etc., are compounds containing 
C, H, and 0, in varying proportions. 

We thus see that chlorine possesses a powerful chemisin 
for hydrogen, even decomposing compounds to obtain it. 
We shall hereafter see that the great chemism of chlorine 
enables it to displace from their binary compounds the 
nearly-allied elements, bromine and iodine. The sulphides 
are also dissociated thus : — 

H 2 S + 2C1=2HC1 + S. 

Chlorine is extensively used as a deodorizer and disin- 
fectant, owing its efficiency to its power of liberating from 
water oxygen, which, as already explained, while in a nas- 
cent state, oxidizes putrefactive vapors and disease germs 
to their destruction. 

Chlorine is soluble in water, l cc of water absorbing 
nearly 3 CC of this gas. It may be condensed to a liquid at 
0° by a pressure of 6 atmospheres, or by 1 atmosphere at 
- 34°. I 1 at 0° and 760 mm weighs 3.173*, and its specific 
gravity is 2.45Q. 

93. Tests for Chlorine. — Free chlorine gas or its 
aqueous solution may be recognized by its color, odor, 
or behavior, as in the preceding experiments. 



CHLORINE AND HYDKOGEN. 97 

CHLORINE AND HYDROGEN. 

Hydrochloric Acid, HC1. 

94. Occurrence and Preparation. — We now come to 
an important and useful acid, the only compound formed 
by hydrogen and chlorine, — hydrochloric acid, HC1. This 
acid rarely occurs in nature, although it is a staple ar- 
ticle of commerce. The following is the general method 
of its preparation : — 

Exp. 74 t. Heat to redness, in a crucible, 5 g of common 
salt, NaCl ; pulverize, and place in a generating-flask. Now 
add 10 g strong sulphuric acid, H 2 S0 4 , and heat gently. Hydro- 
chloric acid, in the form of a gas, is freely given off, and can be 
collected by displacement, or over mercury. 

By passing through two or three wash bottles, it may be 
obtained in aqueous solution, the form in which it is used and 
found for sale. The reaction is : — 

NaCl + H 2 S0 4 = HNaS0 4 + HC1. 

If a larger proportion of salt be used, the reaction may be 
represented by this equation : — 

2 NaCl + H 2 S0 4 = Na 2 S0 4 + 2 HC1. 

As we shall hereafter see, commercial hydrochloric acid 
is almost exclusively obtained as a by-product of the 
alkali works where common " soda " is prepared. 

35. Properties. — Hydrochloric acid gas is extremely 
soluble, l cc water at 0° dissolving no less than 505 cc of this 
gas. Its specific gravity is 1.247, it condenses at — 4° 
under 25 atmospheres pressure, and l 1 weighs 1.632 g . 

The aqueous solution of hydrochloric acid is one of the 
most useful chemicals. It acts upon bases to form chlo- 



98 CHLORINE AND HYDROGEN. 

rides; the principal one of these, common salt or sodium 
chloride, NaCl, occurs in nature in large quantities. The 
gas has a pungent odor. In contact with the air it forms 
dense white fumes, in consequence of its attraction for 
water. The strong water solutions give off the gas read- 
ily ; weak ones may be concentrated by boiling. 

Exp. 75 p. Take three test-tubes. In the first, place a solu- 
tion of silver nitrate, AgN0 3 ; in the second, a solution of nn i 
curous nitrate, HgN0 3 ; and in the third, a solution of plumb i 
acetate, Ph^B^C^. To all three now add hydrochloric acid. 
What takes place ? 

As the silver, lead, and mercurous chlorides are insolu- 
ble in water, it precipitates these metals from solutions 
in which they are contained. Other chlorides, as a rule, 
are soluble. 

This fact is taken advantage of in analyzing unknown 
substances. Suppose, for example, we have a solution 
which may contain any or all known metals. If we add 
hydrochloric acid to it, and get a precipitate, we know 
that one or more of the metals whose chlorides are insolu- 
ble in water must be present. We know, in other words, 
that one or more of the three metals, silver, lead, and 
mercury, must be present; and further, as their chlorides 
are insoluble, we know that the addition of hydrochloric 
acid to the solution removes these metals. By the 
use of other chemical substances, other groups may be 
precipitated in a similar way; and thus the problem o. 
determining what is in the substance under examination 
is more and more narrowed down, until we know exactly 
what is present. Substances which are used for the pur- 
pose of precipitating groups of metals in analysis are 
called Group-Reagents. 



CHLORINE AND OXYGEN. 99 

When hydrochloric acid is mixed with one-third its 
volume of nitric acid, Aqua Regia or nitro-hydrochloric 
acid is produced, which is the strongest solvent known ; 
even gold and platinum are dissolved in it. The great 
power of aqua regia lies in the fact that it readily gives 
up chlorine, which, in a nascent condition, is very active. 
The salts formed by aqua regia are chlorides. In using 
this solvent it should be but slightly warmed ; a stronger 
heat drives off chlorine to waste. 

96. Test for Hydrochloric Acid, or Chlorides. — Their 
solutions, even when acidulated with nitric acid, give a 
white precipitate of silver chloride, AgCl, with silver 
nitrate, AgN0 3 . This precipitate is insoluble in nitric 
acid, and soluble in ammonia. 

Sug. Student, try a solution of NaCl. Write the equation. 

CHLORINE AND OXYGEN. 

97. Chlorine and oxygen unite to form two compounds, 
which have been isolated, viz., — 

Chlorine monoxide . . . . . C1 2 0, 

Chlorine trioxide (?) C1 2 3 (?), 

and Chlorine tetroxide C10 2 . 

- These oxides never occur free in nature, nor can they 
be produced by the direct union of chlorine and oxygen ; 
they may, however, be obtained by indirect processes. 
Since they are unimportant, and dangerous to prepare, 
owing to the ease with ivhich they decompose, we shall 
treat each but briefly. 

98. Chlorine Monoxide, C1 2 0. — This substance is a 



100 CHLORINE AND OXYGEN. 

yellow-colored gas, prepared by passing chlorine gas over 
dry mercuric oxide in the cold, thus : — 

2 HgO + 4 CI = Hg 2 OCl 2 + C1 2 0. 

This gas may be pressed into a U-tube, surrounded with a 
freezing mixture, and condensed to a yellow liquid ; but 
if the tube be suddenly jarred or scratched, as with a file, 
it explodes with great violence. If exposed to the action 
of heat, it is also decomposed, but with less violence. It 
unites with water, thus : — 

C1 2 + H 2 = 2 HCIO. (See Hypochlorous Acid.) 

99 Chlorine Trioxide, C1 2 3 . — This is a greenish-yel- 
low gas, of great instability and explosive power. It can 
be prepared in different ways, one of which is as follows : 
Make a thin paste of 4 parts potassium chlorate, KC10 3 , 
and 3 parts of arsenious oxide, As 2 3 , with water ; place 
in a generating-flask, and add a solution of 12 parts nitric 
acid and 4 parts water ; warm gently. This gas has been 
pronounced by recent investigators to be simply a mixture 
of chlorine and chlorine tetroxide, consequently it is 
doubtful if the trioxide has ever been prepared. Accord- 
ing to theory the trioxide unites with water, forming 
chlorous acid, thus : — 

C1 2 3 + H 2 = 2 HC10 2 . (See Chlorous Acid.) 

100. Chlorine Tetroxide, C1 2 4 or C10 2 . — This is a 
dark-yellow gas of small importance, as it forms no acids, 
and consequently no distinct series of salts (it is also dan- 
gerously explosive); but some idea of its deportment, as 
well as that of the other chlorine oxides, may be gained 
by the following experiment, which may be safely made 
if care be used : — 



THE CHLORINE OXACIDS. 101 

Exp. 76 p. Drop into a test-tube three or four small crys- 
tals of potassium chlorate, KC10 3 ; then, holding the tube with 
a pair of tongs, its mouth turned away from all persons pres- 
ent, add a few drops of strong sulphuric acid. Warm gently, 
when chlorine tetroxide gas will appear ; but a sharp and 
vicious explosion soon terminates the experiment. The con- 
tents of the tube are thrown violently out, but the tube itself is 
seldom broken. Note the odor of the gas. 

THE CHLORINE OXACIDS. 

101. This series contains four acids, none of which are 
of commercial importance, nor are they of special value as 
reagents ; and they all decompose upon standing. Their 
salts, however, are stable, well known, and of great util- 
ity. These acids are : — 

Hypochlorous acid .... HCIO, 

Chlorous acid HC10 2 , 

Chloric acid HC10 3 , 

and Perchloric acid HC10 4 . 

Sug. Student, name the salts these acids form with potassium. 

Hypochlorous Acid, HCIO. 

102. Preparation. — This acid has been prepared only 
in dilute aqueous solution. Owing to its instability, the 
student must prepare it freshly for the purpose of studying 
its properties. It is obtained by treating freshly-precipi- 
tated mercuric oxide, HgO, with chlorine water, thus : — 

3 HgO + 4 CI + H 2 = 2 HgO, HgCl 2 + 2 HCIO. 
Exp. 77 t. Dissolve as much mercuric chloride, HgCl 2 , as 
possible in 250 cc hot water ; then add KOH as long as a pre- 
cipitate (yellowish-red) is formed. You thus obtain the fresb 
mercuric oxide : — 



102 THE CHLOKINE OXACIDS. 

2 KOH + HgCl 2 = HgO + 2 KC1 + H 2 0. 

Filter out this precipitate, and wash it by adding much water 
to it as it lies upon the filter-paper. Finally make a hole 
in the point of the filter-paper, and wash the precipitate through 
into a half-litre flask by means of 250 cc cold water. Then 
gradually add chlorine water, thoroughly shaking meanwhile, 
until the remaining brownish-red precipitate ceases to dissolve 
(i.e., be careful to keep an excess of HgO. If the chlorine 
water be fairly-well saturated, you will require less than 200 cc ) . 
The remaining precipitate is the compound represented b}~ the 
formula HgO, HgCl. Allow the flask to stand in a cool place 
until this precipitate settles, when you will be able to pour off 
the slightly-colored aqueous solution of hypochlorous acid, 
which may be used for experimental purposes. Note the odor 
of the acid differing from chlorine. 

Exp. 78 p. In a florence flask fitted with a bent delivery 
tube, generate chlorine gas from sodium chloride, manganese 
dioxide, and sulphuric acid. Pass this gas into a cold, dilute 
solution of potassium hydroxide, stopping short of saturation. 
You will thus obtain for experimental purposes a solution of 
potassium hypochlorite, KCIO, thus : — 

2 KOH + 2 CI = KCIO + KC1 + H 2 0. 

103. Properties. — Hypochlorous acid, when in dilute 
aqueous solution, is a yellowish liquid, possessing a char- 
acteristic odor and strong bleaching properties. A con- 
centrated solution cannot be distilled without undergoing 
decomposition ; indeed, it soon decomposes at ordinary 
temperatures, of its own accord, giving off chlorine and 
oxygen gases. 

Exp. 79 p. Moisten in dilute hydrochloric acid pieces of 
unbleached cotton cloth and suspend them for a moment in the 
solutions of hypochlorous acid and potassium hypochlorite, as 
prepared above. Finally wash them in pure water, allow them 



THE CHLORINE OXACIDS. 103 

to dry, and note that they are bleached. Also make this 
experiment with a solution of bleaching-powder. 

The hypochlorites are of great importance, especially 
the calcium compound, which is used in bleaching-factor- 
ies under the name of bleaching-poivder. Enormous quan- 
tities of this powder are prepared by passing chlorine gas 
into chambers containing slaked lime, Ca(OH) 2 , thus : — 

2 Ca (OH) 2 + 4 CI . = 2 H 2 + (CaCl 2 + Ca(C10) 2 ). 
It thus appears that bleaching-powder is a mixture of cal- 
cium hypochlorite with calcium chloride. 

The cloth to be bleached, after a thorough cleansing, is 
drawn through a solution of bleaching-powder, and then 
through very dilute sulphuric acid, which decomposes 
the powder, liberating free chlorine in the fibres of the 
cloth. By this means, as previously explained, the color- 
ing-matters are destroyed. The effect, upon hypochlorous 
acid or the hypochlorites, of stronger acids may be seen, 

thus : — 

HCIO + HC1 = H 2 + 2 CI, 
and KCIO + 2 HC1 = KC1 + H 2 + 2 CI. 

104. Tests for Hypochlorous Acid, or the Hypochlo- 

riteso — 1. An aqueous solution of the free acid bleaches 
litmus paper or solution. 

2. The odor of the free acid identifies it. 

3. Hypochlorites in solution require acidulating with an 
acid, as acetic or hydrochloric acid, before they produce 
their bleaching effects. 

Query. Will a hypochlorite bleach when acidified with HNO3? H 2 S0 4 ? 
try it. 

Sug. Carefully distinguish between bleaching a substance and changing 
its color, as from blue to red. When it has been bleached, an alkali will 
not restore the original color; when simply changed, the color may thus 
be restored. 



104 THE CHLORINE OXACIDS. 

Chlorous Acid, HC10 2 . 

105. This acid is probably not known in the free state. 
But its potassium salt, KC10 2 , may be had together with 
potassium chlorate by adding potassium hydrioxide to an 
aqueous solution of chlorine tetroxide. All the chlorites 
are easily decomposed and all the soluble ones possess 
bleaching properties. 

106. Tests for Chlorous Acid and the Chlorites. — 

Test as for a hypochlorite, when the same results are 
obtained. Then to a fresh portion add a small quantity 
of arsenious oxide, As 2 3 , and a drop or two of nitric acid. 
If the solution be that of a hypochlorite, its bleaching pow- 
er is destroyed. If that of a chlorite, it will still bleach. 

Note. This acid and its salts may well be dismissed with simply a 
reading of the two preceding paragraphs. 

Chloric Acid, HC10 3 . 

107. This acid is also unimportant, and, moreover, 
somewhat dangerous to experiment upon ; its prepara- 
tion, therefore, should be omitted. 

Potassium chlorate, KC10 3 , the most important salt of 
chloric acid, is made by passing chlorine into a concen- 
trated, warm solution of potassium hydroxide, KOH : — 
6 CI + 6 KOH = 5 KC1 + 3 H 2 + KC10 3 . 

Query. What takes place when the solution of potassium hydroxide 
is cold and dilute ? 

In order to get the free acid from this potassium salt, 
the latter is treated with a solution of hydrofluo-silicic 
acid, H 2 SiF 6 : — 

2 KC10 3 + H 2 SiF 6 = K 2 SiF 6 + 2 HC10 3 . 



THE CHLORINE OXACIDS. 105 

The potassium salt thus formed is insoluble ; conse- 
quently, after it has subsided, the dilute solution of 
chloric acid may be poured off, and afterwards concen- 
trated in a vacuum over sulphuric acid. 

Concentrated chloric acid is, indeed, a powerful oxidiz- 
ing agent, uniting so eagerly with vegetable tissue, as 
paper and wood, that it ignites them. 

Sug. Student, name the uses of KC10 3 as suggested by the experi- 
ments up to this point. 

108. Tests for Chloric Acid and the Chlorates, — 

1. Free concentrated chloric acid may be recognized by 
its odor and by its charring a slip of paper. 

2. The dry chlorates, when treated with strong sul- 
phuric acid, yield a yellowish, explosive gas, C1 2 4 (see 
Exp. 76); with hydrochloric acid, they yield free chlorine 
gas. (Exp. 69.) 

Perchloric Acid, HC10 4 . 

109. This acid and its salts are also of but small impor- 
tance, and the free acid should not be prepared. It is to 
be had by distilling dry potassium perchlorate, KC10 4 , 
with strong, boiled sulphuric acid. Perchloric acid is 
one of the most powerful oxidizing agents known. When 
dropped upon charcoal, it explodes with violence, while 
dry wood and paper are instantly ignited. Upon the skin 
it produces deep and dangerous wounds. 

One of its salts, potassium perchlorate, may be prepared 
as follows : — 

Exp. 80 p. Heat in a generating-flask 5 g potassium chlorate, 
carefully noting when the oxygen ceases readily to be evolved, 
and the mass becomes pasty or semi-solid, — 

2 KCJ0 3 = KC1 + KC10 4 +2 0. 



106 EXERCISES IN CHLORINE. 

Remove the heat, allow the flask to cool, and dissolve its con 
tents in much hot water. Upon cooling, the potassium per- 
chlorate separates out in crystals, while the potassium chloride 
remains in solution. These crystals may be removed, dried, 
and used for experimental purposes. 

110. Tests for Perchlorates. — 1. Dry perchlorates 
yield no yellow explosive gas with sulphuric acid, and 
with hydrochloric acid yield no free chlorine. 

2. They require for their decomposition a higher tem- 
perature than the chlorates. 



CHLORINE AND NITROGEN. 

111. Chlorine and nitrogen unite to form dangerous ex- 
plosives, which rival nitro-giycerine, and whose composition 
is represented by the formulae, NH 2 C1, NHC1 2 , NC1 3 . They 
are prepared by passing a current of chlorine through a 
moderately warm solution of ammonium chloride. Under 
no circumstances should the student thus bring these chemi- 
cals together. The eminent chemists, Dulong, Davy, and 
Faraday, were seriously maimed while experimenting with 
these capricious compounds. 

EXERCISES IN CHLORINE. 

1. Given: NaCl, H 2 S0 4 , Mn0 2 , HgO, As 2 3 , and KOH. From these 
chemicals show how you could prepare chlorine and all the eompounds 
treated in this chapter. 

2. Prob. How many tons of salt, NaCl, would it require to prepare 
10 tons of hydrochloric acid ? 

3. Prob. How many litres of chlorine gas can be obtained from 75 k 
of NaCl when the barometer reads 755 mm and the thermometer 18° C. 1 

4. How are acids formed from their anhydrides 1 

5. Given: The formula of an acid to determine the formula of its 
anhydride. Proceed thus : 2 HN0 3 — H 2 = N 2 5 . In a like manner 



EXERCISES IN CHLOKINE. 107 

determine the anhydrides of HC10 4 , HN0 2 , H 2 S0 4 , HCIO, HC10 3 , and 
HI0 3 . 

0. What per cent of HC1 is hydrogen 1 Chlorine ? 

7. Determine the percentages of H, N, and O in the nitrogen oxacids. 

8. Prob. 20 1 of CI, measured at standard temperature and pressure, 
increased to 20.5 1 owing to a fall in the barometer. How many millimetres 
did the barometer fall ? 

9. Chlorine gas was discovered in 1774. Who was its discoverer 1 He 
used the chemicals HC1 and Mn0 2 . Describe the process, and write the 
equation. 

10. An aqueous solution of chlorine changes, upon standing, to an 
aqueous solution of HCL What gas is liberated 1 Write the equation. 

11. How can you prepare chlorine gas from bleaching-powder 1 

12. The water analyst, in determining by titration the amount of 
chlorine in drinking-water, proceeds thus : He first prepares a standard 
solution of silver nitrate, by dissolving 4.79° AgN0 3 in l 1 of distilled water ; 
he then measures out 100 cc of the drinking-water, and adds sufficient potas- 
sium chromate, K 2 Cr0 4 , to tinge the water light-yellow. Now, from a 
burette graduated to tenths of a cubic centimetre, he adds to the water 
thus prepared the standard silver solution, drop by drop, with constant 
stirring, until the red color at first formed in the liquid becomes perma- 
nent. The number of cubic centimetres silver solution added is equal to 
the number of milligrams of chlorine per -^ litre. How much silver 
nitrate does l cc of the standard solution contain? How much silver? 
Show how this amount of silver will precipitate l m § of chlorine. (Suo. 
108 m s s of Ag precipitate 35.5 m s s of CI ; therefore, to precipitate l m s of CI 
requires 108 -4- 35.5 = 3.03 m s s Ag.) The permanent red color is due to the 
formation of silver chromate, Ag 2 Cr0 4 ; this formation does not occur 
until the chlorine is all precipitated. The potassium chromate thus serves 
as an indicator, showing when the right amount of AgN0 3 has been added. 
Why does the silver unite with the chlorine first ? 

General Note. Recent investigators doubt the existence in a frep 
state of chlorine trioxicle. 



CHAPTER VII. 

BROMINE, ITS OCCURRENCE, ETC. — THE BROMINE ACIDS. 

BROMINE. 
Symbol Br'. — Atomic Weight, 80 ; Specific Gravity, 3.1872. 

112. Occurrence. — Bromine does not occur in a free 
condition, but is found combined with magnesium, sodium, 
potassium, and perhaps with some organic compounds, as 
bromides in sea water, certain mineral waters, and in most 
saline deposits. It also occurs combined with silver in 
the silver mines of Mexico and South America. 

Balard, in 1826, discovered bromine in sea water. He 
obtained it from the concentrated solution or " mother 
liquor" from which the crystals of common salt, NaCl, 
had been removed. 

Bromine, although by no means a plentiful element, is, 
nevertheless, an article of commerce, considerable quanti- 
ties of it being produced from the concentrated " mother 
liquors " of salt wells in various parts of the world. The 
United States produces the greater part of the commercial 
article. 

113. Preparation. — Exp. 81 p. Dissolve in a test-tube a 
crystal of potassium bromide, KBr ; add a small quantity of 
chlorine water. Notice that the liquid turns somewhat darker 
than the chlorine water added ; this is due to free bromine. 
Now add three or four drops of carbon bisulphide, CS 2 , and 



BROMINE. 109 

shake thoroughly. What color does the carbon bisulphide 
assume ? 

Exp. 82 t. Thoroughly mix 30 g granulated manganese di- 
oxide, Mn0 2 , with 40 g potassium bromide, KBr, and place in a 
retort. Use the same apparatus as for nitric acid, excepting 
that the condenser must contain 0.4 1 cold water, and the neck 
of the retort must dip below the water in the condenser ; or a 
rubber cork with a bent tube dipping below the water may be 
fitted into the neck of the retort. Now T pour into the retort 
105 g sulphuric acid, H 2 S0 4 , previously diluted with 70 cc water, 
and warm gently. Bromine will distil over in reddish-brown 
fumes and condense under the water in the condenser. A part 
of the bromine will also be dissolved in the water, thus giving 
bromine and bromine water at one operation. Save them both, 
each in separate bottles accurately fitted with ground glass 
stoppers, and keep in a cool place. 

Query. The specific gravity of the H. ; S0 4 is 1.84. How many cubic 
centimetres equals 10.5s ? 

Bromine is best prepared for class purposes by treating 
potassium bromide, KBr, with manganese dioxide and 
sulphuric acid, thus : — 

3 H 2 S0 4 + 2 KBr + Mn0 2 = MnS0 4 + 2 HKSO, + 2 H 2 + 2 Br. 

Sug. Student compare this equation with that given in Preparation of 
Chlorine, Art. 90. 

Bromine is liberated when occurring in saline waters, 
by adding a small quantity of manganese dioxide, and 
then just enough sulphuric acid to liberate sufficient 
chlorine to free the bromine. This process depends upon 
the fact that free chlorine gas liberates bromine from its 
compounds. 

Query. Which possesses the greater chemism, chlorine or bromine 1 



110 BROMINE AND HYDROGEN. 

114. Properties of Bromine. — Bromine is a dark-red 

colored liquid, at ordinary temperatures always giving off 
pungent, irritating fumes. It bleaches organic coloring- 
matter, but not so powerfully as chlorine. Its principal 
use is as a disinfectant. 

Bromine has a specific gravity of 3.1872 at 0°, freezes at 
- 7.5°, and boils at + 59.3°. 

Note. When removing the stopper of a bottle containing bromine or 
its aqueous solution, always turn your face away. Why ? 

115. Tests for Free Bromine. — 1. Free Bromine, even 
in dilute solutions, when shaken (in a test-tube) with 
carbon disulphide, CS 2 , colors the latter brownish-red. 

2. Colors ether yellowish-red, which color is destroyed 
by shaking with potassium hydroxide, KOH. 

3. Colors starch-paste solution orange-yellow. 

Sug. Student make these tests upon a dilute solution of the bromine 
water prepared as above. Also try the bleaching effect as with chlorine. 



BROMINE AND HYDROGEN. 

116. Hydrobromic Acid, HBr, is the only acid formed 
by bromine and hydrogen. It is unimportant to the be- 
ginner, and he should not attempt its preparation. It is 
usually obtained by allowing liquid bromine to act upon 
amorphous phosphorus and water. This is accomplished 
by placing 10 parts of liquid bromine in a stoppered 
funnel provided with a stop-cock to allow the bromine to 
fall drop by drop into a generating-flask containing one 
part phosphorus and two parts water: — 

P + 5 Br + 4 H 2 = H 3 PO, + 5 HBr. 

What takes place in this reaction can best be understood 



BKOMINE AND HYDROGEN. Ill 

by considering it in two phases. When bromine acts 
upon phosphorus the two unite directly, forming either 
phosphorus tribromide, PBr 3 , or the pentabromide, PBr 5 , 
according to the relative quantity of bromine present. 
Now each of these compounds is decomposed by water, as 
represented in the following equations : — 

PBr 3 + 3 H 2 = H 3 P0 3 + 3 HBr ; 
PBr 5 + 4 H 2 = H 3 P0 4 + 5 HBr. 

Thus, in each case, all the bromine appears finally in 
combination with hydrogen in the form of hydrobromic 
acid. 

We should naturally expect that the simplest method 
for making hydrobromic acid would be like that used for 
making hydrochloric acid, but strong sulphuric acid decom- 
poses hydrobromic acid, and hence, although the reaction, 

2 KBr + H 2 S0 4 = K 2 S0 4 + 2 HBr, 

actually does take place, a further reaction also takes 
place, as follows : — 

2 HBr + H 2 S0 4 = 2 H 2 -f- S0 2 + 2 Br, 

giving the gas, sulphur dioxide, S0 2 , and free bromine in 
the form of vapor, and from these it is very difficult to 
separate the hydrobromic acid. 

This acid is a colorless, irritating gas whose chief inter- 
est to us lies in the fact that it yields the salts called 
bromides^ some of which are applied to useful purposes, 
thus: silver bromide, AgBr, is used in photography; 
potassium bromide is used in medicine ; while others, as 
magnesium bromide, MgBr 2 , are much esteemed ingredi- 
ents of certain mineral springs. 

Hydrobromic acid is used in organic laboratories, and it 
is now an article of commerce. 



112 BROMINE AND HYDROGEN. 

117. Tests for the Bromides. — 1. Place the solution 
in a test-tube, and liberate the bromine by means of 
chlorine water; then add a few drops of carbon bisul- 
phide, CS 2 , and shake thoroughly. The carbon bisulphide 
is colored brownish-yellow. 

Note. An excess of CI must be avoided, otherwise a chloride of 
bromine is formed which does not color the bisulphide. 

2. With silver nitrate, AgN0 3 , this solution gives a 
yelloivish-ivhite precipitate, AgBr, insoluble in nitric acid, 
difficultly soluble in ammonia, and easily soluble in potas- 
sium cyanide, KCy. 

Query. How do HC1 and the chlorides deport themselves with AgX0 3 , 
etc.? 

Note. When bromides and nitrates occur in the same solution, the 
tests interfere. The bromine may be readily detected, but not so the nitrates, 
since the H 2 S0 4 and FeS0 4 liberate free bromine which obscures the ring. 

Sug. Student try a bromide as if testing a nitrate. 

118. Bromine, Oxygen, and Hydrogen. — No com- 
pounds of bromine and oxygen have been isolated, but 
two, and possibly three, acids have been prepared, viz : — 

HBrO, Hypobromous acid, 
HBr0 3 , Bromic acid, 
and HBr0 4 , Perbromic acid (?). 

In regard to the existence of the last there is much doubL 
These acids never occur in nature, and are of small 
importance to the beginner, so we shall here notice them 
but briefly. 

119. Hypobromous Acid, HBrO, may be prepared in 
the same way as hypochlorous acid, HCIO, thus: — 

HgO + 4 Br + H 2 = HgBr 2 + 2 HBrO. (See HCIO.) 



BROMINE AND HYDKOGEN. 113 

It possesses bleaching powers, is of a straw-yellow color, 
and easily breaks up into water, bromine, and oxygen. 

Query. What salts does this acid form % 

120. Bromic Acid, HBr0 3 , is formed by treating silver 
bromate, AgBr0 3 , with bromine water, thus: — 

5 AgBr0 3 + 6 Br + 3 H,0 = 5 AgBr + 6 HBr0 3 . 
The salts (bromates) formed by this acid somewhat re- 
semble the chlorates in their properties, but are of little 
importance commercially. 

Exp. 83 p. The easiest way to get a bromate is to dissolve 
bromine in a strong solution of potassium hydroxide, when a 
mixture of potassium bromate and bromide is formed : — 

6 Br + 6 KOH = 5 KBr + KBr0 3 + 3 H 2 0. 
The bromate will soon separate out in crystals, which the 
student may try as he did the chlorates. 

121. Tests for the Bromates. — 1. They are decom- 
posed by hydrochloric acid, giving free bromine (which 
may be detected as in Art. 115). 

Query. What effect does HC1 have upon KC10 3 ? 

2. The bromates yield no explosive gas with sulphuric 
acid, but they are decomposed, affording free bromine and 
oxygen. 

Query. How does H 2 S0 4 affect the chlorates ? 

EXERCISES IN BROMINE. 

1. What chemicals are needed to prepare bromine and its compounds? 

2. What per cent of KBr is potassium ? Bromine ? 

3. How many grams of NaBr would be required to prepare 10s Br ? 

4. Compare the bromine and chlorine acids from a commercial stand- 
point. 



114 BROMINE AND HYDROGEN. 

5. What does the word Bromine signify ? 

6. In analyzing a sample of mineral water, a chemist found 0.1678§ 
bromine per litre. In combining his bases and acids he united this bro- 
mine with magnesium. How many grams per litre of magnesium bromide, 
MgBr 2 , did he report ? Ans. 0.1929s. 

7. How many grams of chlorine gas would be required to free the 
bromine of one gram KBr ? (KBr+ Cl = KCl-f Br.) 

8. To precipitate all the bromide in 50 cc of a solution, required 0.21 5s 
silver nitrate. How much bromine per litre did the solution contain ? 
Sug. 108 parts Ag precipitate 80 parts Br. 

9 Try to prepare HBr by passing H 2 S through bromine water. 
Explain the equation, — 

H 2 S + 2Br=2HBr + S. 

Filter the solution and test for HBr. Can you prepare HC1 by passing 
H 2 S through chlorine water ? Write the equation. 

10. Boil in an evaporating dish a mixture of solid K 2 Cr 2 7 and H 2 S0 4 
until the mixture turns bright red. When cool, place a portion of the 
substance thus formed in a test-tube fitted with a bent delivery tube, and 
add a solid chloride, as NaCl. Note the bright brownish-red gas evolved : — 

4 NaCl + K 2 Cr 2 7 + 3 H 2 S0 4 = 2 CrQ 2 Cl 2 + 2 Na 2 S0 4 + K 2 S0 4 + 3 H 2 0. 

Now lead this gas, which becomes plentiful by applying a gentle heat, into 
a test-tube containing a dilute solution of ammonia. Note the yellow 
liquid formed : — 

2 NH 3 + 2 H 2 + Cr0 2 Cl 2 = (NH 4 ) 2 CrQ 4 + 2 HC1. 

Acidify this solution with acetic acid, and add lead acetate : — 

Pb(C 2 H 3 2 ) 2 + (NH 4 ) 2 CrQ 4 = PbCrQ 4 + 2 NH 4 C 2 H 3 2 . 

Note the yellow precipitate thus obtained. 

Thus try with KBr instead of NaCl. What results ? Try the same 
with a mixture of KBr and NaCl. Do you obtain the same reaction as 
with NaCl alone 1 How can you distinguish a chloride in presence of a 
bromide 1 See Douglas and Prescott, Qual. Anal., p. 159. 



CHAPTER VIII. 

IODINE. THE IODINE ACIDS. — SEPARATION OF CHLO 

RIDES, BROMIDES, AND IODIDES. FLUORINE. — HYDRO 

FLUORIC ACID. 

IODINE. 

Symbol I r . — Atomic Weight, 127; Specific 
Gravity, 4.948. 

122. Occurrence. — Iodine, like bromine and chlorine, 
does not occur free. It is chiefly obtained from sea water, 
from which it is taken up by seaweeds. These weeds, 
especially on the coasts of Ireland and Scotland, are 
washed ashore during storms ; then they are collected, 
placed in shallow trenches, dried and burned in thin 
layers so that the temperature may not rise high enough 
to vaporize the iodides of sodium, potassium, etc., con- 
tained in the ashes or kelp, as it is popularly termed. 
These iodides are soluble in water, and are removed, by 
washing, from the ashes. Small quantities of bromides 
are also obtained in this process. Plantations of this sea- 
weed are cultivated in some parts of the ocean, and at 
the proper times vessels are sent to collect the weed. 

Iodine also occurs together with Chili saltpetre in the 
form of sodium iodide, Nal, and of late a considerable 
quantity of that which comes into the market has been 
obtained from this source. It also occurs as silver iodide, 
Agl, in certain American silver mines. 



116 IODINE. 

123. Preparation. — Exp. 84 p. Treat a crystal of potas- 
sium iodide, KI, as in Exp. 81. What results do you obtain? 

Exp. 85 t. It is not necessary to prepare iodine for class 
purposes, since it is an article of commerce, procurable at any 
drug store. It may be readily obtained, however, by treating 
potassium iodide, KI, with manganese dioxide and sulphuric 
acid, as in preparing bromine and chlorine. The iodine vapors 
may be condensed in a suitable flask surrounded by a cooling 
mixture. 

Commercial iodine is prepared from the iodides by 
treating them, as above, in iron retorts, when it is 
liberated in violet vapors and condensed in black, shining 
crystals upon the sides of suitable condensers : — 
2 KI + Mn0 2 + 3 H 2 S0 4 = MnS0 4 + 2 HKS0 4 + 2 H 2 + 2 1. 

Sug. Compare this equation with that for bromine and chlorine. 

124. Properties. — Exp. 86 p. Heat a small crystal of 
iodine in a test-tube. What is the color of the vapor? Note 
the odor. 

Iodine at ordinary temperatures is a black, shining 
solid, possessing a decidedly metallic appearance, and 
always giving off fumes of a peculiar odor. When heated, 
iodine is easily converted into vapor of a splendid violet 
color and characteristic odor. The specific gravity of this 
vapor is 8.72. 

Queky. Courtois discovered iodine in the year 1811. He named it 
from lododyjs, violet-colored. Why did he thus name it ? 

Iodine is much used in medicine for various purposes- 
especially in reducing swellings, such as goitre and weep- 
ing sinews. It is also used in checking the spread of 
eruptive diseases, like erysipelas. When thus applied it 
is used in the form of a solution prepared by taking, by 



IODINE AND HYDROGEN. 117 

weight : iodine, 20 parts ; potassium iodide, 30 parts ; 
water, 900 parts. Free iodine when brought in contact 
with the skin turns it brown. 

Iodine is only slightly soluble in water, but easily 
soluble in alcohol, carbon bisulphide, chloroform, and in 
an aqueous solution of potassium iodide. 

125. Tests for Free Iodine. — 1. Free iodine colors 
carbon bisulphide, CS 2 , violet. 
2. Colors starch paste blue. 

Note. Those substances heretofore mentioned as coloring a solution 
of starch paste and potassium iodide blue, produce this effect by liberat- 
ing iodine which unites with the starch to form a blue substance. 

Query. What substances act in this way 1 



IODINE AND HYDROGEN. 

126. Hydriodic Acid, HI, is the only compound of 
hydrogen and iodine. This is a colorless gas resembling 
hydrochloric acid. It is of no commercial importance, owing 
to its instability. Its principal use is for organic work and 
as a blow-pipe reagent. 

Exp. 87 p. Suspend in a test-tube half full of cold water a 
few crystals of iodine. Pass through this solution sufficient 
sulphuretted hydrogen, H 2 S (Art. 167), to decolorize it. Hy- 
driodic acid will be formed and sulphur deposited : — 

H 2 S + 2 1 = S + 2 HI. 
The sulphur will soon subside, and the clear solution of the acid 
amy be poured off. Reserve this solution for the next experiment. 

Hydriodic acid may also be made by the method 
which was described under hydrobromic acid; that is, by 
gradually adding iodine to amorphous phosphorus under 



118 IODINE AND HYDBOGEN. 

water. The reactions are the same as in the case of 
bromine, the iodides of phosphorus being first formed, 
but afterwards decomposed by the water. 

Exp. 88 p. In one test-tube place a solution of mercuric 
chloride, HgCl 2 ; in another, a solution of silver nitrate, AgN0 3 ; 
in a third, a solution of lead acetate, Pb(C 2 H 3 2 ) 2 . To each of 
these now add a portion of the hydriodic acid solution prepared 
as above. Note the brilliantly colored precipitates which are 
respectively the iodides of mercury, silver, and lead. Repeat 
the experiment, using a solution of potassium iodide, KI, in 
place of the acid. Do you obtain the same results ? 

Hydriodic acid unites with bases to form the iodides, 
many of which are valuable. Some of these iodides 
possess very bright and distinctive colors which are of 
service in identifying some of the metals whose salts are 
in the solution to be analyzed. Since the acid itself is 
unstable and somewhat troublesome to prepare, the chem- 
ist preferably uses a solution of potassium iodide for this 
purpose. 

Sug. Explain these equations : — 

HgCl 2 + 2 HI = Hgl 2 + 2 HC1 ; 
Pb(C 2 H 3 2 ) 2 + 2 HI= Pbl 2 + 2 HC 2 H 8 2 ; 
AgN0 3 + HI = Agf -f HN0 3 . 
41so write the same equations with KI in place of HI. 

127. Tests for Hydriodic Acid or the Iodides. — 1. To 

the solution add chlorine water. Then add a few drops 
of carbon bisulphide and shake. Iodine is freed and colors 
the bisulphide violet. 

Note. If the iodide is not readily soluble, the iodine may he freed by 
warming the insoluble iodide in a test-tube with a crystal of potassium 
chlorate and hydrochloric acid; the bisulphide may then be directly 
added. 



IODINE AND HYDROGEN. 119 

2. With silver nitrate, AgN0 3 , a yellow precipitate is 
given, insoluble in nitric acid; sparingly soluble in am- 
monia; soluble in potassium cyanide, KCy. 

Sug. Compare this test with the similar ones for chlorine and bromine. 

Query. Which test in the case of chlorine is distinctive ? Of bro- 
mine ? Of iodine ? 

Note. Solutions of iodides and nitrates do not readily yield a test for 
nitric acid for the same reasons as those given under bromine. The test 
for the iodide is readily obtained. Try a solution of KI as for a nitrate. 
Try a solution of KI and KBr with CS 2 , etc. Which test do you obtain ? 

128. Detection of Chlorides, Bromides, and Iodides 
in the same Solution. — The student is probably aware 
that the precipitates obtained with silver nitrate do not 
afford sufficiently marked characteristics to distinguish 
these compounds, and that the carbon bisulphide tests also 
fail, especially in the case of bromides in presence of 
iodides. To separate and distinguish these substances is 
not an easy task, and of the many ways proposed, none 
are entirely satisfactory and at the same time simple and 
convenient. The following method requires careful ma- 
nipulation. 

Exp. 89 j?. Let us suppose the solution to contain NaCl, 
KBr, and KI. Divide it in three portions and add to numbers 
1 and 2 an excess of silver nitrate, when the precipitates ob- 
tained in each will consist of AgCl, AgBr, and Agl. Filter 
out these precipitates and wash them thoroughly with hot water, 
then wash them through a hole in the point of the filter-paper 
into separate beakers. To the first beaker now cautiously add 
but two or three drops of potassium bromide, and to the second 
carefully add three or four drops of potassium iodide, and boil 
for a short time. Again filter the contents of the first beaker, 
and test the clear liquid which' runs through for chlorides, 



VZi) IODINE, OXYGEN, AND HYDROGEN. 

Art. 96. Filter the contents of the second beaker, and test the 
solution for bromides (Art. 117, 1). 

Try a part of the third portion directly for iodides by Art. 
127, 1. In case you do not succeed, proceed thus : To the re- 
mainder of the third add a few drops of ferrous sulphate, 
FeS0 4 , and copper sulphate, CuS0 4 , when a light-green pre- 
cipitate of cuprous iodide, Cu 2 T 2 , will be thrown down. Test 
this insoluble iodide by Art. 127, 1, Note. 

Explanation. What occurs in the three cases may thus be ex- 
plained : — 

1. In number 1, AgCl + AgBr + Agl + KBr = Agl + 2 AgBr + KCL 
The KBr and AgCl react, yielding KC1, which is soluble and in the solution 
tested for chlorides. 

2. AgCl + AgBr + Agl + 2 KI = 3 Agl + KBr + KCL 
The KC1 and KBr are soluble and readily yield the test for bromides. 

3. This last is readily understood when we remember that the iodine is 
partially precipitated in the Cu 2 I 2 . 

Note. The foregoing method is not sufficiently accurate for quanti- 
tative determinations where an excess of potassium bromide or iodide 
would necessarily be employed. Care must be used to avoid an excess 
of either reagent when employed for qualitative work. 



IODINE AND OXYGEN. 

129. There is but one known oxide of iodine, Iodine 
Pentoxide, I 2 5 . This oxide may be obtained by heat- 
ing iodic acid, HI0 3 as described in the next article. 



IODINE, OXYGEN, AND HYDROGEN. 

130. There are but two oxygen acids of iodine, viz: 

Iodic Acid, HI0 3 , 
Periodic Acid, HI0 4 . 



IODINE, OXYGEN, AND HYDROGEN. 121 

These acids and their salts are unimportant; we shall 
therefore notice only the first, and that but briefly. 

Exp. 90 op. Heat one part, by weight, of free iodine with 
ten parts strong nitric acid (sp. gray. 1.5) until reel fumes cease 
to come off and the iodine is dissolved. Eyaporate the solution 
to dryness and heat in the air-bath to 200°. The resulting 
white powder is iodine pentoxide. 

The first product formed in this process is iodic acid, 
HIOo. When this acid is heated to 200° it breaks up into 
water and iodine pentoxide : — 

2HI0 3 = I 2 O s + H 2 0. 

By again dissolving the pentoxide in water, pure iodic 
acid may be obtained. 

Sug. "Write the equation for the action of iodine on nitric acid, 
remembering that NO, HI0 3 , and H 2 are formed. Also show the action 
of H,0 on I,0 5 . 

Iodic acid rapidly oxidizes organic substances. When 
this acid or the pentoxide is heated with powdered char- 
coal, phosphorus, sulphur, etc., it oxidizes them so rapidly 
that the action is accompanied by flame. 

It forms normal salts, the iodates, as KI0 3 . Acid salts, 
as KIO0HIO3 or HK(I0 3 ) 2 , are also known. 

131. Tests for Iodic Acid or the Iodates. — To a 

solution containing either the free acid or its salts add 
starch paste and chlorine water; no change in color 
occurs. Now add a solution of sodium sulphite, K"a 2 SO s , 
when iodine is liberated and the solution turns blue. 



122 FLUORINE, 



FLUORINE. 



Symbol, F'. — Atomic Weight, 19 ; Specific 
Gravity, 1.313. 

132. Occurrence. — Fluorine is a greenish gas. It 
occurs combined with calcium as calcium fluoride, CaF 2 , 
or fluor spar, in cubical crystals which are usually some- 
what translucent and often quite transparent. It also 
occurs in the mineral cryolite, which is a fluoride of 
sodium and aluminium. Other sources of fluorine are 
unimportant. 

Fluorine has, until recently, resisted all attempts to 
isolate it, and they have been many. This fact appears 
to be due to its great chemism (in the presence of water) 
when nascent, at which time it attacks the vessel in 
which it is generated. It has been prepared by elec- 
trolyzing dry hydrofluoric acid in platinum tubes. 

Fluorine forms no oxides, no oxygen acids, and but oijo 
hydrogen acid, viz. : — 

Hydrofluoric Acid, HF. 

133. Preparation. — This acid is also a gas correspond- 
ing to hydrochloric, hydrobromic, or hydriodic acid. It 
is best prepared by treating calcium fluoride in a leaden 
evaporating-dish, with sulphuric acid : — 

CaF 2 + H 2 S0 4 = CaS0 4 + 2 HF. 

This gas is a dangerous poison, and great care must be 
exercised in its preparation. 

134. Properties. — Exp. 91 t. Pulverize 4 g calcium fluor- 
ide, and place in a leaden disk, which can be made by cutting 



FLUOKINE. 123 

oft a piece of lead pipe, splitting it open lengthwise, and then 
placing it in an iron mortar where it can, by the aid of an iron 
pestle, be hammered out into the shape of an evaporating-dish. 
Next prepare a sheet of glass by coating both sides with 
beeswax or paraffin. Upon one side of this glass engrave, by 
means of a pin or sharp, soft wire, some design. Now put 
the evaporating-dish, supported by a ring-stand, in a gas- 
chamber or where there is a current of air to carry off all 
fumes, and support the plate a short distance above the dish. 
Add strong sulphuric acid to the calcium fluoride, when hydro- 
fluoric acid will be quickly liberated, especially if a gentle heat 
be cautiously applied. In a few minutes the design will be 
neatly etched into the glass. Be very careful not to inhale any 
hydrofluoric acid fumes, as they are exceedingly poisonous. 

Hydrofluoric acid is often employed as above in etching 
thermometer scales. 

This acid seems to have great chemism for such sub- 
stances as calcium, silicon, and potassium, in consequence 
of which glass is immediately attacked and can not be 
used to store the gas or its aqueous solution. Leaden or 
vulcanite bottles are employed for this purpose. 

The action of hydrofluoric acid upon sand and glass, 
which is a compound of sand with bases, is largely due to 
the action represented by the equation , — 

SiO a + 4 HF = 2 H 2 + SiF 4 . 

The silicon tetrafluoride, SiF 4 , thus formed, escapes as a 
gas. 

135. Tests for Hydrofluoric Acid in Fluorides. — The 

best is the etching test, "but care must be taken not to 
scratch the glass with the graver used in cutting through 
the wax. 



124 EXERCISES IN IODINE AND FLUOEINE. 



EXERCISES IN IODINE AND FLUORINE. 

1. How many grams of silver nitrate would be required exactly to 
combine with 10s of potassium iodide ? 

2. How many pounds of iodine can be obtained from one-half ton oi 
sodium iodide ? 

3. What chemicals are necessary to prepare from potassium iodide 
iodine and its compounds ? 

4. Make a comparison between the commercial values of the acids of 
chlorine, bromine, and iodine. 

5. Compare the same three elements according to their physical con- 
ditions at ordinary temperatures ; also according to their atomic weights, 
specific gravities, and chemism. Make a table comprising the acids they 
form. 

6. Will nitro-hydrochloric acid liberate bromine and iodine from their 
compounds ? Try it. 

7. Class prepare a sheet of glass as directed in Exp. 91, writing the 
names of the class through the wax. Under the teacher's direction etch 
with HF. This will be a good memento to leave in the Laboratory. 

8. Test a solution of NaCl and KN0 3 for the different acids combined 
with bases in these salts. 

9. Under potassium and sodium learn the tests for these metals, and 
try for them in the above solution. 

10. It would now be well for the student to practise daily upon 
unknown solutions, as in 8 and 9. These solutions should not contain acids 
that interfere, and the bases with which the acids are combined should 
preferably be potassium, sodium, and ammonium. 

11. In working upon an unknown solution a student obtained tests 
for K, Na, NH 3 and H 2 S0 4 , HC1, and HN0 3 . What salts may have been 
dissolved in the solution ? In case the laboratory contains only NH^NOg, 
NH 4 C1, KN0 3 , KC1, NaCl, and K 2 S0 4 , what salts may the teacher have 
employed in preparing this solution ? 

12. See Trans. Roy. Soc. Canada, 1883, sec. 3, pp. 65 et seq., for " Hy- 
driodic Acid as a Blow-pipe Beagent." Dr. HaanePs paper on this topic 
is accompanied by very fine plates. 

13. To a solution containing an iodide and a bromide add CS 2 ; now 
by the addition of sufficient chlorine water try to obtain first the color for 
iodme, and second the color for bromine.- Explain. 



CHAPTER TX. 

Carbon. — Carbon and Hydrogen. — Oxides oi 
Carbon. — Carbonic Acid. — Cyanogen. — Prussic 
Acid. 

CARBON. 

Symbol C iv . — Atomic Weight, 12. — Specific Gravity: Dia- 
mond, 3.5-. 6 ; Graphite, 2.25; Charcoal, 1.57. 

136. Occurrence. — Carbon is a very widely distributed 
element, occuring chiefly in an impure state or in chemical 
compounds. It is an important constituent of all organic 
substances, mineral carbonates, carbonic acid gas, and the 
cyanides. In a free condition, it exists in three widely 
differing forms. 

1. In pure, transparent, glittering, octahedral crystals, 
as Diamonds, which are found in earthy detritus or clayey 
shales in Africa, South America, Australia, and other 
localities. 

Sug. Write an essay on diamond-mining, diamond-cutting, and famous 
diamonds. 

2. In dark, shining, six-sicled slabs as Graphite, Plum- 
bago, or Black Lead, which occurs in England, Ceylon, 
the United States, and other countries. 

3. In impure forms as Coal, Soot, and Lamp-black. Of 
coal we find a number of varieties, as Charcoal, Anthracite 
coal, Bituminous coal, etc. 

Sug. Write a short paper on coal-mining. 



126 CARBON. 

137. Preparation. — It is not necessary to prepare car- 
bon for class illustration, since any of the above-named 
modifications are easily to be obtained. 

Small diamonds have been made artificially by dissolv- 
ing carbon in molten iron and then cooling it under pres- 
sure. The method of their formation in nature is not 
understood. 

Graphite has been frequently observed in iron-smelting 
furnaces, having been artificially produced at high tem- 
peratures. 

In Exp. 2, Charcoal was obtained by heating wood in a 
test-tube. The principles therein involved are made use 
of in preparing charcoal for commerce. In practice the 
wood is heated in closed iron cylinders, or burned in 
large pits or kilns with a limited supply of air. In the 
latter case a part of the wood thus treated is completely 
consumed in order to furnish the heat requisite for charring 
the remainder. 

Lamp-black or soot is prepared by burning a carbonaceous 
substance, such as oil, resin, etc., in a limited supply of air. 
The lamp-black appears as a black smoke which is easily 
collected upon a cold surface. 

Queries. What makes a lamp smoke ? Why is the lamp-chimney 
blackened ? Explain the deposition of soot in stovepipes and chimneys. 
Can soot be obtained from the Bunsen flame ? Luminous flame ? Alcohol 
flame ? Ordinary candle flame % Why does pitch-pine give such a smoky 
flame ? If one wishes to know a fact which comes within the province of 
Experiment, how should he proceed ? 

138. Properties. — Carbon is absolutely indispensable 
to all organic structures. With other elements, such as 
hydrogen, oxygen, and nitrogen, it is capable of forming 
an almost endless number of chemical compounds. As a 
matter of convenience these are generally considered 



CARBON. 127 

under the head of the Chemistry of the Compounds oj 
Carbon, or Organic Chemistry. 

Carbon has many industrial uses. It is chiefly used in 
reducing metals from their ores and for heating and 
illuminating purposes. 

The colorless diamond is highly prized as a jewel. A 
colored variety is used in glass-cutting, while its dust is 
employed for polishing hard and refractory substances. 
Drills armed with diamond points are used by miners and 
others ; these drills will quickly cut through the hardest 
rocks. Smoky or black diamonds and carbonado, an 
impure massive form, are principally used for this latter 
purpose. 

The diamond is the hardest substance known, its value 
in the " scale of hardness," by which mineralogists estimate 
the hardness of minerals, being 10°. This scale, in which 
each substance is able to scratch all that are below it in 
the scale, is as follows : — 



Diamond 10° 

Sapphire 9° 

Topaz 8° 

Quartz 7° 

Feldspar 6° 



Apatite 5° 

Fluorspar 4° 

Calcspar 3° 

Gypsum . .... 2° 

Talc 1° 



The primary form of a diamond crystal is octahedral : 
but it occurs in many different forms derived from this 
primary crystal. When first removed from its matrix, the 
diamond is often rough and lustreless, and -afterwards 
requires cutting and polishing ; this latter is accomplished 
by means of its own dust. Like all hard substances it is 
brittle and quite easily broken. In acids and alkalies the 
diamond is completely insoluble. When heated to a high 
temperature in a current of oxygen it burns, the product 
being carbon-dioxide gas, C0 2 , with a small amount ol 



128 CARBON. 

residual ash. Upon light the diamond exerts a very high 
refractive influence, to which property it owes its great 
brilliancy. 

Query. What properties cause the diamond to be so highly esteemed 
as a jewel ? 

Graphite is greasy to the touch. It is largely used for 
polishing purposes, such as for coating shot and powder, 
and, owing to its great permanence in the air, is largely 
employed in the manufacture of stove-polish. Its particles, 
however, are very hard, and the saws used in cutting it are 
quickly worn out, and a knife, when employed for the same 
purpose, soon loses its edge. 

Graphite, owing to its great infusibility, is now mixed 
with clay and extensively used in making crucibles which 
are employed by metallurgists, while its employment in 
the manufacture of leads for the common lead-pencil is 
a well-known application. 

Sug. Prepare a paper on the manufacture of lead-pencils. 

Coal is probably the remains of a magnificent vegeta- 
tion which flourished during the carboniferous age. It 
has been brought into its present condition by heat and 
pressure. The heat is thought to have been supplied by 
the heated interior of the earth, while the pressure was 
due to the influence of water and the rocks which subse- 
quently formed above the coal. This explanation con- 
templates the idea that during some post-carboniferous 
subsidence which swept over the globe, the land sank 
down, and the vegetation was overwhelmed by the inflow 
of water, while the rocks were afterward deposited. The 
ashes and " clinkers" of burned coal are the mineral 
sediments which were entangled by the vegetation, as 
well as the mineral constituents of the plants themselves. 



CARBON. 129 

Anthracite coal is used for heating purposes, and for 
reducing metals from their ores. Its reducing power 
depends upon the chemism of carbon for oxygen. 

Query. What is meant by reduction ? 

Bituminous coal differs from anthracite in that the 
former contains more hydrogen-carbon compounds, and 
evidently has not been subjected to so high a temperature 
or to so great a pressure by natural agencies. This variety 
of coal burns with a very hot and sooty flame, and needs a 
large supply of air for its combustion. 

Coke is a form of carbon obtained by driving off, at a 
high temperature, the volatile constituents of coking- 
coal. It is left behind in the retorts when coal is distilled 
for the purpose of making illuminating gas. 

Gas Carbon is also produced in distilling coal. This 
form of carbon is much used in making negative plates 
for batteries and for the terminals of electric lamps. 

Peat is a form of fuel nearly akin to bituminous coal, 
and is formed from the roots and stems of certain plants 
growing in bogs or marshes. 

Lignite is a peculiar form of coal formed from such 
sources as our present deciduous trees, and often exhibits 
a distinctly woody structure. 

Jet is a black variety of lignite, much used in jewelry. 
Jet readily takes a high polish. 

Lampblack is much used as a paint, and in making 
printers' ink. 

Charcoal is employed as a reducing agent in preparing 
iron from its ores. Sugar-charcoal, coal-tar, etc., when 
heated with lime in the electric furnace, yield calcium 
carbide, CaC 2 , which promises to be of value in manu- 
facturing acetylene gas for illuminating purposes. 



130 CARBON. 

Charcoal possesses some remarkable properties: — - 

Exp. 92 p. Place a filter-paper in a funnel ; then fill the 
paper nearly full of bone-black or freshly-burnecl charcoal 
powder. With a filter thus arranged see if you can produce 
any changes in the following solutions by filtering them several 
times: 1. Vinegar; 2. Syrup of brown sugar; 3. Dilute black 
molasses; 4. Indigo solution; 5. Carmine solution; 6. Beer; 
7. Potassium dichromate solution. 

Queries. What changes occurred ? Does 7 behave like the others ? 
Why ? Explain the changes. 

We thus see that charcoal is capable of decolorizing 
and purifying such organic liquids as were mentioned. The 
reason why it is employed in filtering drinking-water is 
now apparent. It is supposed that this action of charcoal 
is partially due to the fact that it absorbs oxygen, and 
possesses the power of causing certain organic substances 
to combine with this oxygen. However this may be, 
the charcoal soon loses its efficacy unless it be frequently 
washed and exposed to the air. For the same reason 
charcoal will destroy the gases from putrefying sub- 
stances. 

Queries. Why should a filter be frequently cleaned ? Is it best con- 
tinuously to keep a filter full of water ? What is the use of gravel in 
filters ? Why should a rapid river flowing over stones and with numerous 
falls be purer than one with a sluggish current and a sandy or muddy 
bottom ? 

Exp. 93 p. Place in an evaporating-dish a few grains of 
common sugar ; acid a few drops of strong sulphuric acid. Do 
you obtain carbon? Also thus try starch. What results? 

From the above experiment and from previous work 
the student may learn that many substances, such as 
sugar, oils, resins, fats, waxes, tallow, and alcohol are 



CARBON. 131 

compounds of carbon. We may add to this list nearly 
every substance used as food by man and by animals, and 
all the vegetable drugs known to chemistry and com- 
merce. We should not forget also that it is to the 
compounds of carbon that we are indebted for our rai- 
ment, and even for a portion of our dwellings. 

Query. How could we obtain light without the aid of carbon ? 

Kerosene, gasoline, naphtha, benzine, and paraffin are 
all derived from Petroleum, or rock oil, which is a 
mixture of many compounds of carbon and hydrogen 
found in company with coal deposits. The limits of our 
work forbid a further notice of these interesting sub- 
stances. 

139. Tests for Carbon. — 1. Free carbon, as soot, coal, 
lampblack, etc., may be recognized by its physical proper- 
ties and by its insolubility in all acids and alkalies ; also 
by the manner in which it burns when heated on platinum 
foil. 

2. Graphite may be recognized by its properties, and by 
the black, insoluble streak which it leaves when drawn 
across paper. 

Sug. Write with a lead-pencil on white paper. Try to bleach it. What 
results 1 

3. The diamond is recognized by its brilliancy and 
hardness, being able to produce a scratch upon the hard- 
est substance. 

Query. The hardness of glass is less than 6°. Is the fact that a 
given substance makes a scratch upon glass sufficient evidence that it is a 
diamond ? 



132 CARBON AND HYDROGEN. 

CARBON AND HYDROGEN. 

140. Carbon and Hydrogen form many compounds, 
but three of which we shall notice here : — 

1. Methane, or Marsh Gas, CH 4 ; 

2. Ethylene, or Olefiant Gas, C 2 H 4 ; 

3. Acetylene, C 2 H 2 . 

Methane, CH 4 . 

141. Methane, or Marsh Gas, may thus be prepared for 
illustration : — 

Exp. 94 p. 2 g fused sodium acetate, N"aC 2 H 3 2 , are heated in 
a hard glass test-tube fitted with a jet, with 8 g sodium hydroxide, 
NaOH, and 2 g finely-powdered quick -lime, CaO. As soon as 
the gas issues freely from the jet it may be ignited, when it 
burns with a bluish-yellow, non-luminous flame. The reaction 

NaC 2 H 8 2 + NaOH = Na 2 C0 3 + CH 4 . 

Query. What purpose does the CaO serve 1 (Compare the use of 
Mn0 2 in producing oxygen from KC10 3 .) 

This gas occurs free in nature, and is formed in stagnant 
pools by the decay of leaves and other vegetable material, 
whence it derives its name, Marsh Gas. It also occurs in 
coal seams and in coal mines, where it is known as Fire 
Damp. Methane condenses at —10° under 50 atmospheres, 
and boils at — 160° under 1 atmosphere. 

Exp. 95 p. Discharge the hydrogen pistol by means of a 
mixture of marsh gas and air. 

When mixed with air or oxygen, methane is often the 
cause of most violent explosions. To prevent these ex- 
plosions, Sir Humphrey Davy invented his Safety Lamp, 
which consists of an ordinary lamp, the flame of which is 



CARBON AND HYDROGEN. 133 

surrounded with a wire-gauze cage. This cage prevents the 
temperature of the surrounding mixture of methane and 
air from rising to the point of ignition. The specific 
gravity of methane is 0.558. 

Query. Why does the wire gauze placed between the Bunsen flame 
and chemical vessels prevent them from breaking % 

Sug. Student ascertain the particulars of several noted colliery ex- 
plosions. 

Exp. 96 p. Hold moistened strips of red and blue litmus 
paper in a jet of methane. The gas does not affect them. 

We are thus led to the conclusion that methane does 
not resemble either the acid or the alkaline gases already 
studied. These compounds of carbon and hydrogen differ 
in many respects from the compounds of other elements 
with hydrogen. A very large number of the hydrogen- 
carbon compounds is known and new ones are being con- 
stantly discovered. We may regard as derived from these 
the compounds treated in organic chemistry. 

Since methane is not readily acted upon by reagents, the 
color of its flame, and its explosiveness when mixed with 
air, will answer our purposes as tests. 

Ethylene, or Olefiant Gas, C 2 H 4 . 

142. Ethylene is formed in distilling coal, and is, there- 
fore, a constituent of coal gas. It is prepared most readily 
by the following method, which may be shown for class 
illustration : — 

Exp. 97 t. Heat in a generating-flask fitted with a jet 
delivery-tube 10 g of ethyl alcohol, C 2 H 6 0, with 50 g strong 
sulphuric acid. Note the odor and taste of the gas issuing 
from the jet, and then ignite it. It burns with the ordinary 



134 CARBON AND HYDROGEN, 

gas-flame. The sulphuric acid simply abstracts one molecule 
of water from the alcohol, thus : — 

C 2 H 6 = H 2 + C 2 H 4 . 

Query. How many cubic centimeters of alcohol and acid are required 
above, the specific gravity of H 2 S0 4 being 1.843 and that of ordinary 
alcohol being 0.815 ? 

Ethylene is explosive when mixed with three times its 
volume of oxygen. 

Query. What substances are formed ? Student write the equation. 

When equal volumes of ethylene and chlorine gases are 
brought together, an oily liquid, called " Dutch Liquid," 
C2H4CI2, the odor of which resembles chloroform, is formed. 

The specific gravity of ethylene is 0.9784; it can be 
condensed to a liquid at 10° by a pressure of 51 atmos- 
pheres, and boiling under 1 atmosphere at — 100°. 

143. Test for Ethylene. — Fill a jar with the gas sup- 
posed to contain ethylene ; then pass a current of chlorine 
gas into the jar. If the oily Dutch Liquid mentioned 
above be formed, ethylene is present. 

1 Note. This liquid is insoluble in water. 

Acetylene, C 2 H 2 

144. Acetylene is also a gas, and possesses a powerful 
and disagreeable odor, which is particularly noticeable 
when an ordinary Bunsen burner strikes back and con- 
tinues to burn at the base. 

It has been prepared by passing sparks from a powerful 
battery through an atmosphere of hydrogen, the termi- 
nals of the electrodes being carbon. It is now cheaply 
prepared by the action of calcium carbide on water. It 



CARBON AND HYDROGEN. 135 

burns with a bright, luminous flame, and has a specific 
gravity of 0.92. The odor of acetylene betrays its 
presence. 

145. Illuminating" Gas is obtained, together with many 
bye-products, by distilling coal in retorts. It contains 
hydrogen, methane, and ethylene, and many other hydro- 
carbon compounds. It also contains in small quantities 
the impurities: ammonia; hydrogen-sulphide, H 2 S; carbon 
dioxide, C0 2 ; carbon monoxide, CO; atmospheric oxygen; 
and nitrogen. These impurities are mostly removed by 
passing the gas through a series of washing and absorbing 
reagents. 

Sug. Student visit the gas works. Write a description of the process 
of gas manufacture. Consult R. and S. 

The student may test for these impurities thus : — 

1. Ammonia is detected by holding a strip of moistened 
faintly-red litmus paper in a stream of the illuminating gas. 
The paper turns blue if ammonia be present. 

2. Hydrogen sulphide wili blacken a strip of bibulous paper 
moistened with lead acetate, Pb^CsE^O^, when the paper is 
held in a current of the gas. 

3. Carbon dioxide may be detected b}~ shaking lime-water, 
Ca(OH) 2 , in a flask of the gas (see test for C0 2 ). 

4. Oxygen may be detected as directed under tests for 
oxygen. Art. 29, 2. 

5. The nitrogen and carbon monoxide cannot be detected with 
certainty by any means likely to be at the beginner's disposal. 

Coal Tar. — It has been mentioned that there are many 
bye-products formed in distilling coal in the manufacture 
of illuminating gas : of these coal tar is, from a chemical 
standpoint, the most remarkable. It is used directly for 



136 CAKBON AND OXYGEN. 

various industrial purposes which are so well known as 
to need no description. The attention of many chemists 
has been given to this substance, and from it they have 
produced a large number of articles which are in daily 
use in the arts and manufactures. The beautiful aniline 
anthracine and naphthaline dyes are obtained from this 
source, and their production has revolutionized not only 
the art of dyeing, but also the industries of whole coun- 
tries, and made it possible for even the laborer to em- 
bellish his home with colors which before were only 
accessible to the opulent. 

Water-gas. — By passing steam over coke heated above 
600° C, a mixture of carbon monoxide and hydrogen or 
water-gas is obtained. Burning water-gas produces a 
high temperature, but when used as an illuminant it is 
first carburetted ; i.e. it is mixed with the vapors of coal 
oil and again subjected to heat. This process increases 
the luminosity of the flame. 

CARBON AND OXYGEN. 

146. There are two oxides of carbon, viz : — 

1. Carbon Monoxide, CO ; 

2. Carbon Dioxide, C0 2 . 

Of these two oxides the latter is to us of the greater im- 
portance. Both are gases under ordinary conditions. 

Carbon Monoxide, CO. 

147. Preparation, etc. — This gas is a product of com- 
bustion, and is formed when carbon is burned in a limited 

supply of oxygen : — 

c + O = CO, 



CAKBON AND OXYGEN. 137 

It is also formed at high temperatures by the action of 
carbon on carbon dioxide : — 

C0 2 + C = 2 CO. 

Query. Of what kind of action is this an example 1 

Exp. 98 p. Carefully heat in a generating-flask with a de- 
livery-tube, 2 g potassium ferrocyanide. K 4 FeCy 6 , with 20 g strong 
sulphuric acid. Ignite the stream of escaping gas, CO ; care- 
fully note its odor, if any, and the color of the flame. 

Carbon monoxide burns with a lambent blue flame, as 
seen in coal stoves when the supply of air is limited, and 
at the upper surface of the coal in grate fires. The com- 
bustion at the bottom of the coal first produces carbon 
dioxide; this substance coming in contact with the heated 
coal near the upper surface is reduced to carbon monoxide; 
and when this latter meets the air above the coal, it again 
burns, forming carbon dioxide, the combustion now being 
complete : — ■ 

CO + o = co 2 . 

Carbon monoxide is colorless and tasteless, and has a 
faint and peculiar odor. It acts upon the animal economy 
as a deadly poison, producing headache, giddiness, and 
insensibility. It seems to produce its effects upon the 
system by combining with the haemoglobin of the blood, 
leaving traces which betray its action even after death. 
Great care should be taken not to allow this poisonous 
gas to accumulate in rooms warmed by coal fires. One 
per cent is a sufficient quantity to prove fatal. The joints 
of the stove should be tight, the draft strong, and, above 
all, the ventilation should be perfect. Death has been 
produced from warming poorly-ventilated rooms by means 
cf charcoal fires in open vessels from which carbon mon- 



138 CARBON AND OXYGEN. 

oxide is given off ; and people have perished by going to 
sleep beside a lime or brick kiln or a charcoal pit, being 
suffocated and poisoned b)^ the gaseous oxides of carbon. 

Carbon monoxide unites with iron and nickel to form 
carbonyl compounds. Nickel carbonyl, Ni(CO) 4 , is a gas 
which deposits nickel when heated to 200°. Commercial 
nickel may be obtained by this reaction. 

Carbon monoxide has a specific gravity of 0.968, and 
condenses at — 139.5°, under a pressure of 35.5 atmos- 
pheres ; under 1 atmosphere it boils at — 190°. 

148. Test for Carbon Monoxide. — This gas may be 

recognized, when present in sufficient quantity, by its 
bluish flame. 

Cakbon Dioxide, C0 2 . 

149. Occurrence. — This gas, commonly known as car- 
bonic acid gas, occurs widely distributed in nature. It 
occurs free in the atmosphere in small but persistent 
quantities, and combined in all the carbonates, from which 
it is readily liberated by the stronger acids. Calcium 
carbonate, or limestone, CaC0 3 , is a very plentiful sub- 
stance. Whole geological formations consist of this 
material. It also is the chief constituent of shells and 
most corals. Whole islands are being constantly built 
up by the corals in the tropical regions. 

Sug. Write a paper on coral formations. 

150. Preparation. — Exp. 99 p. In a wide test-tube or 
a small beaker place about 5 CC calcium hydroxide solution, 
Ca(OH) 2 . By means of a small glass tube force air from the lungs 
through the solution, when a white precipitate will be formed. 
Continue to breathe some minutes through the liquid ; the pre- 
cipitate dissolves. 



CARBON AND OXYGEN. 139 

This white precipitate is calcium carbonate, CaC0 3 , 
and was produced by the action of the carbon dioxide 
which is thrown out of the lungs as a waste product at 
every respiration : — 

Ca(OH) 2 + C0 2 = CaC0 3 + H 2 0. 

Large quantities of carbon dioxide must thus neces- 
sarily be liberated in the air, since it is produced in the 
same way by all air-breathing animals. 

Query. Why does the air in poorly-ventilated living-rooms contain 
more carbon dioxide than those that have good ventilation ? 

Exp. 100 p. Carefully lower into a wide-mouth bottle a 
burning taper. When the taper is extinguished, add a small 
quantity of calcium hydroxide ; cork the bottle, and shake. 
Do you again obtain the white precipitate ? 

All carbon compounds when burning in the air produce 
carbon dioxide. This gas is also emitted during volcanic 
action. 

Query. In what ways may C0 2 be liberated in living-rooms ? 

Exp. 101 p. To a dilute solution of sugar or molasses in 
water add a little bakers' }~east. Place in an evaporating-dish 
a small quantity of this solution ; also fill a test-tube with the 
solution, invert the tube, and place its mouth below the solution 
in the evaporating-dish. The whole is now to be left standing 
in a warm place. Fermentation soon begins, bubbles of gas 
rise in the tube, and the liquid is forced down. When the tube 
is full of gas, pour the latter out into another tube (as if it were 
water), add calcium hydroxide, and shake as before. Is the 
gas carbon dioxide ? 

Carbon dioxide is also produced in fermentation, and 
in the spontaneous decomposition of animal and vegetable 
substances. 

Query. In what ways is carbon dioxide liberated in the atmosphere ? 



140 CARBON AND OXYGEN, 

Exp. 102 p. Break into pieces about 10 g calcium carbonate^ 
or marble, CaC0 3 . Place in a generating-flask, and cover with 
water. Fit the flask with a V-shaped delivery-tube, and collect 
the materials mentioned in the following experiments. Upon 
adding hydrochloric acid to the contents of the flask, carbon 
dioxide will be plentifully given off, although a gentle heat 
may sometimes be required. The equation is : — 

CaC0 8 + 2 HC1 = CaCl 2 + H 2 + C0 2 . 

Note. The CaCl 2 solution should be evaporated to dryness, fused in 
a sand crucible, and kept in a tightly-corked bottle. It is useful for 
drying gases and for other purposes. 

Carbon dioxide may be readily obtained in larger quan- 
tities by treating the carbonates with strong acids. With 
the gas which the student is now ready to prepare he may- 
proceed to study the 

151. Properties. — Exp. 103 p. Fill a wide test-tube with 
carbon dioxide. Note the odor and color, if any, and try the 
effect upon a glowing match ; a burning match ; a lighted 
taper. What results? Try to ignite a jet of this gas. 

Carbon dioxide is a colorless, odorless gas which does 
not support combustion. Advantage has been taken of 
this fact in making an engine to extinguish fires. The 
gas is generated from sodium carbonate, Na 2 C0 3 , and sul- 
phuric acid, and allowed to escape through a hose. 

Sug. Explain the construction of a Babcock fire extinguisher. Write the 
equation for the reaction of Na 2 C0 3 and H 2 S0 4 . For HNaC0 3 and H 2 S0 4 . 

Exp. 104 p. In the centre of a pine ruler 2 cm wide and 
100 cm long drive two needles. This ruler will serve as the 
beam of a balance, while the needle-points will serve instead of 
a knife-edge bearing. These points are to be placed upon a 
flat metallic surface. Now from one end of the beam suspend, 
by means of a thread, a small paper sack, and from the other 



CAKBCXN ASD OXYGEN. 141 

end a larger paper sack. Into the smaller sack carefully drop 
small pieces of iron, chalk, sand, or any heavy substance, until 
the beam is in equilibrium. Into the larger sack now deliver a 
jet of carbon dioxide. The larger sack will soon become 
heavier and sink. 

Queries. With what gas was the larger sack filled before introducing 
the C0 2 ? Is C0 2 lighter or heavier than air? Suppose the sack be sus- 
pended mouth downwards, what would occur if a jet of hydrogen were 
allowed to flow up into it ? In what other way have you compared the 
weight of air with that of gases ? How should ajar be placed when filling 
it with C0 2 , mouth down or up ? 

Exp. 105 p. Place a lighted taper in an open jar of air. 
Now fill a second jar with carbon dioxide, and then pour the 
contents of this jar into the first. As soon as the taper is 
immersed in carbon dioxide it is extinguished. Try to transfer 
by means of a siphon the contents of a jar of carbon dioxide 
into another arranged with a taper like the first, treating the 
gas as if it were a liquid. 

Carbon dioxide is heavier than air, its specific gravity 
being 1.529. I 1 at 0° and 760 ram weighs 1.965 s . It can be 
condensed to a liquid by pressure or by reduction of its 
temperature. Under one atmosphere it liquefies at —78°; 
a still further reduction, which may be accomplished by 
allowing the liquid to escape into a box with a sieve-like 
bottom, freezes the liquid to a snow-like solid. 

Exp. 106 op. Place any small animal in a jar of carbonic 
acid gas ; note the symptoms and time of death. Also thus 
proceed with a jar of carbon monoxide. How do the symptoms 
compare ? The time of death ? 

Pure carbon dioxide seems to produce its deadly effects 
by asphyxiation, the lungs being unable to effect the 
decomposition of the gas, and thus to appropriate the 
needed oxygen, which it certainly contains, but holds with 



142 CARBON AND OXYGEN. 

an exceedingly tenacious grasp. As one would infer, this 
gas is very stable; but its decomposition can, nevertheless, 
be accomplished,, 

Exp. 107 p. Into a jar of carbon dioxide place a brightly 
burning magnesium ribbon. It continues to burn. Is carbon 
set free? Also try a piece of burning sodium. Is the gas 
again decomposed ? Are other products than carbon formed ? 
If these products are MgO and Na 2 0, write the equations. 

Since carbon dioxide is liberated in so many different 
ways, it is present in the atmosphere in considerable 
quantities. It varies from 2.7 to 3.5 volumes in 10,000 
volumes of air. This gas is more plentiful in living-rooms 
than out of doors, but the amount present should never 
be allowed to exceed 7 or 8 parts per 10,000. It is not 
so much that carbon dioxide is itself very poisonous, as 
that other and more dangerous animal impurities are 
thrown off by the lungs together with the carbon dioxide. 
We may therefore practically employ the amount of car- 
bon dioxide present in a living-room as an index to meas- 
ure the purity of the air, as will hereafter be explained. 

Prob. Calculate the number of cubic metres of C0 2 in the 
atmosphere, assuming the extent of the air to be as stated 
under Atmosphere. Compute its weight. 

Carbon dioxide gas is often found in mines, caves, old 
wells, and vats. When so occurring it is termed Choke 
Damp, and many persons yearly lose their lives through 
a lack of caution in entering such places. Before ventur- 
ing into a place where choke damp is likely to occur, it is 
best to lower a lighted candle ; should the candle be ex- 
tinguished, it is unsafe to go in. A well may sometimes 
be freed from choke damp by dashing in much water, the 



CARBON AND OXYGEN. 143 

gas being thus absorbed; and, again, a vat may be made 
safe by making an opening in the bottom. Why? 

Carbon dioxide is indispensable to plant life. It can be 
shown that in sunlight the leaves, roots, and green parts 
of plants absorb carbon dioxide and give off oxygen ; also 
on moonlight nights and under the influence of the electric 
light the same processes go on more slowly ; but, in the 
dark, carbon dioxide is given off, and oxygen is quite 
freely absorbed. 

Sug. Devise an experiment to show the effect of a growing plant, in 
sunlight, upon carbon dioxide. 

Queries. Are plants in a living-room conducive to health % In a 
sleeping-room ? How are plants and animals interdependent through 
carbon dioxide and oxygen ? What prevents the excessive accumulation 
of carbon dioxide in the atmosphere 1 What would result if all the 
oxygen of the air were consumed ? All the carbon dioxide ? If there 
were an excess of the latter gas 1 

Exp. 108 p. Fill a bottle of about l 1 capacity with water, 
and invert it over the pneumatic trough, or better, over a basin 
of pure water. Now fill the bottle three-fourths full of carbon 
dioxide. Cork the bottle with its mouth under water ; remove, 
and shake it thoroughly. Again place the mouth of the bottle 
under water, and uncork. Does the water rise in the bottle ? 
Is carbon dioxide soluble in water? Reduce the temperature 
of the bottle by means of a freezing mixture, and shake as 
before. Again remove the cork under water. Does a greater 
diminution of the volume of the gas take place? Boil a portion 
of the water in the bottle, and test by adding calcium hydroxide 
(Art. 151). Does the boiled water give a reaction? Testa 
portion of the water in the bottle, with blue litmus paper. Is it 
acid? Taste of the water in the bottle, or drink of it if you 
wish. How does it taste? 

Note. The gas for this experiment should be washed through a 
solution of sodium carbonate. Why? 



144 CARBON AND OXYGEN. 

Although carbon dioxide is injurious when inhaled, it 
is, nevertheless, when taken into the stomach, sometimes 
an aid to digestion. Certain springs and artesian wells 
owe their excellent properties to the carbon dioxide 
absorbed in their waters, while soda water is simply pure 
water highly charged (under pressure) by this gas* 

Sug. Examine and describe a soda-water fountain. 

Queries. What causes the effervescence of champagne? Beer? 
Cider ? What effect does vinegar produce upon common baking-soda ? 
Can you thus generate carbon dioxide ? What causes dough or " empty- 
ings " to rise ? By what process is the gas furnished in this latter case 7 
What is meant by heavy bread ? 

Carbon dioxide is soluble in cold water, l cc of water 
at 0° dissolving about 1.8 CC of the gas; if the pressure be 
increased, the solubility is also increased. An increase 
of the temperature of the water drives off the gas, the 
process being complete at 100°. 

Queries. What Exp. shows that limestone is soluble in water contain- 
ing free carbon dioxide, but insoluble in water containing none of this gas ? 
How is the deposition of limestone formations to be explained ? How 
the crust formed in the tea-kettle ? The formation of caves ? 

When carbon dioxide is passed into water, the solution 
is slightly acid, and it is believed that an acid of the 
formula H 2 C0 3 is thus formed : — 

C0 2 + H 2 = H 2 C0 3 . 

We also consider that the carbonates, such as calcium 

carbonate, are derived from this acid. The acid itself, if 

it exist at all, is very unstable, thus breaking up when 

liberated : — 

H 2 C0 3 = H 2 + C0 2 . 

The carbonates, however, are very stable and of great 



CARBON AND NITROGEN. 145 

importance, and they occur, as previously noted, in im- 
mense quantities. 

152. Tests for Carbon Dioxide and the Carbonates. 

— 1. The free gas is detected by conducting it through a 
solution of calcium hydroxide, Ca(OH) 2 , with which it 
forms the white precipitate, calcium carbonate, CaC0 3 . 

2. The free gas in water solution may be detected by 
adding the same solution as before. 

3. The carbonates will effervesce with any strong acid, 
preferably nitric or hydrochloric acids, yielding free carbon 
dioxide, which may be tested as in 1. 



carbon and nitrogen. 

Cyanogen. 

153. Cyanogen, CN or Cy, is the only known compound 
of carbon and nitrogen. It has been isolated ; but its 
constituents do not directly unite to produce it. The 
cyanogen compounds, as potassium cyanide, KCy, prussic 
acid, HCy, and other substances containing the group of 
atoms, CN, are of importance. 

Cyanogen gas is prepared by heating mercuric cyanide, 
HgCy 2 , in a hard glass test-tube provided with a delivery- 
tube so arranged that the gas may be collected over 
mercury. It is soluble in water, and can be condensed at 
moderate temperature under a pressure of four atmos- 
pheres. It possesses an agreeable odor resembling peach 
blossoms, and burns with a purple flame. This gas is so 
poisonous that the student should hesitate to experiment 
with it. 

The specific gravity of cyanogen gas is 1.806. 



146 CARBON AND NITROGEN. 

Hydrocyanic or Prussic Acid, HCN or HCy. 

154. Prussic Acid is one of the most deadly poisons 
known. It acts so quickly that antidotes are of little use, 
though in some cases ammonia and chlorine have been of 
service in counteracting its effects. It is formed by the de- 
composition of amygdalin, a complicated substance which 
occurs in the leaves of some plants, and. in the kernels of 
peach pits, bitter almonds, and other fruits. It can be 
prepared in a pure, liquid state by passing hydrogen sul- 
phide gas, H 2 S, over mercuric cyanide, HgCy 2 : — 

HgCy 2 + H 2 S = 2 HCy + HgS. 

It should be remembered, however, that this acid is a 
volatile liquid, and that its vapors are a deadly poison and 
instantaneously fatal if inhaled in any considerable quanti- 
ties. The deadly effects of even dilute hydrocyanic acid 
may be illustrated by the following experiment which 
would better by far be omitted : — 

Exp. 109 op. Dissolve 9 g tartaric acid, 4 H 6 O 6 , in 60 cc of 
water ; place in a 70 cc flask, and add 4 g potassium cyanide, KCy. 
Shake, and allow to settle, when a dilute solution, containing 
about 3.6 per cent prussic acid, will b^ obtained (R. and S.). 
Administer to a cat about a teaspoonful, and note effects. 

The specific gravity of hydrocyanic acid at 18° is 0.6969. 

Note. See larger manuals for the remaining numerous compounds of 
cyanogen. The more important cyanides of the metals will be noted 
under the metals in question; but the student is not to forget that many 
of them are extremely poisonous. 

155. Tests for Hydrocyanic Acid and the Cyanides. 

— 1. Prussic acid, HCy, when in dilute solution, may be 
thus detected : To the solution add ammonium sulphide, 



EXERCISES IN CARBON. 147 

NH 4 HS, and evaporate nearly to dryness on the water- 
bath. Ammonium sulphocyanate, NH 4 SCy, is formed ; this 
substance, when dissolved in water and treated with ferric 
chloride, Fe 2 Cl 6 , turns to a deep-red color. 

2. To detect a cj-anide in solution, add a few drops of 
potassium hydroxide, KOH, and then add ferrous sul- 
phate ; shake well, and acidify with hydrochloric acid, when 
prussian blue will be formed if a cyanide be present. 

Sug. Use a solution of KCy for these tests. 

EXERCISES IN CARBON. 

1. Prepare carbon from 10 different articles of food. 

2. Write a short description of the carboniferous age in respect to the 
condition of the atmosphere and vegetation. (Consult some text-book 
on Geology.) 

3. Collect snail shells, clam shells, oyster shells, and a few specimens 
of limestone, and test for carbonates. 

4. Prob. The temperature of the laboratory is 72° F., and the barom- 
eter reads 752 mm . How many litres of C0 2 gas may be generated from 
25s CaC0 3 q How many grams of HC1 are necessary ? How many grams 
of CaCl 2 will be produced 7 

5. Pill a common clay pipe with walnut, hickory-nut, or butternut 
meats. Seal the bowl by means of a thick paste of plaster of paris and 
water. Allow the paste to dry, then heat the bowl in the Bunsen flame. 
Ignite the gas which soon issues from the stem, and prove that it contains 
hydrogen and carbon. 

Sug. Hold a cold glass tube over the flame. Also hold a piece of 
cold porcelain against the flame. 

6. Produce carbon from marble, snail shells, etc. 

7. The value of a sample of coal for reducing iron from its ores is 
ascertained by making the following quantitative determinations • 1. Moist- 
ure; 2. Volatile matter; 3. Fixed carbon, 4. Ash; 5. Phosphorus; 6. Sul- 
phur. The first four determinations may be made thus : Place in a 
weighed porcelain crucible about 5s of the coarsely-powdered sample, and 
heat at 100° for several hours. Weigh, and note the loss of weight as 
" Moisture." Lute on the cover of the crucible by means of a paste of 
wood ashes, leaving a very small opening in one side. Allow the luting 



148 EXERCISES IN CARBON. 

to dry, and weigh the whole. Now heat to redness for one hour; weigh, 
and the loss in weight equals the "Volatile matter." The last weight 
minus the weight of crucible and luting equals the weight of "Coke." 
Now remove the cover, carefully clean off the luting, and weigh again; 
then burn the residue in the crucible, and weigh, noting the loss of weight 
as "Fixed carbon." The last weight minus the weight of crucible equals 
the " Ash." The value of a coal partly depends upon the amount of fixed 
carbon it contains. (See Sulphur and Phosphorus.) 

8. For valuable information concerning the varieties of coal, coal 
analysis, etc., see Dana's System of Mineralogy, pp. 751-760. 

9. As previously stated, it is customary to measure the amount of 
carbon dioxide as an index to the purity of the atmosphere of a room. 
This is accomplished by titration; and a litre-flask and two reagent solu- 
tions are required. 

The first solution consists of 5§ barium hydroxide, Ba(OH) 2 , dissolved 
in l 1 of distilled water; the second, 2.863s pure freshly-crystallized oxalic 
acid, H 2 C 2 4 (H 2 0) 2 , in the same amount of water. From the manner of 
using this latter solution, l cc corresponds to l m s carbon dioxide. 

The litre-flask is filled, by several puffs of a hand-bellows, with the air 
to be tested, and the temperature of the room carefully noted. A quantity 
of the first solution, equal to the space above the litre-mark on the neck of 
the flask, is now added, and the flask vigorously shaken. A portion of the 
solution in the flask is neutralized, — 

Ba(OH) 2 + C0 2 = BaC0 3 + H 2 0, 
and a portion is unchanged. The remainder is now carefully neutralized 
"by means of the second solution, — 

Ba(OH) 2 + H 2 C 2 4 ,(H 2 0) 2 = BaC 2 4 + 4 H 2 0, 
and the number of cubic centimetres is carefully noted ; a phenol phthalein 
solution is employed as an indicator. An amount of the first solution 
equal to that placed in the flask is now directly titrated with the second 
solution, and the number of cubic centimetres of the latter noted. It is 
evident that the difference between the two numbers thus obtained equals 
the number of milligrams of C0 2 per litre. 

Queries. Why do we take 2.863s oxalic acid ? Having the number 
of milligrams C0 2 per litre, multiply the result by 10, and then calculate 
the number of cubic centimetres per 10,000. What principles apply ? 
What is titration ? An indicator ? 

10. The student who wishes to obtain a clearer insight into the 
processes employed in the Chemistry of the Carbon Compounds, will do 
well to consult Dr. Remsen's work on that subject. 



CHAPTER X. 

MOLECULES. — MOLECULAR FORMULAE. — VALENCE. 

156. Molecules. — What is meant by the word atom 
has already been explained. The chemical atom is the 
smallest particle of an element that can take part in 
chemical reactions. Now, if we consider any chemical 
compound as, for example, hydrochloric acid, it is clear 
that the smallest particle of this compound which can be 
imagined must contain both hydrogen and chlorine, and 
must contain at least one atom of each of these elements. 
Such a smallest particle of a compound is called a 
molecule. 

The molecules of compound bodies are made up of 
atoms of different kinds. The molecules of the elements 
are made of atoms of the same kind. The theory com- 
monly held is that when the elements exist in the free 
state their atoms unite to form molecules. 

The formulae which we use to represent compounds are 
intended to represent molecules, just as the symbols of 
the elements are intended to represent atoms. Thus the 
formulae H 2 0, NH 3 , HC1, HN0 3 , etc., represent the mole- 
cules of water, ammonia, hydrochloric and nitric acids ; 
and we see from them that the molecule of water is made 
up of 2 atoms of hydrogen and 1 of oxygen ; that the 
molecule of ammonia consists of 1 atom of nitrogen and 3 
atoms of hydrogen, etc. Knowing the weights of the 



150 MOLECULES. 

atoms which make up a molecule, we know the weight of 
the molecule. It is the sum of the weights of the atoms 
contained in it. The molecular iv eight of water is 18, 
which is the sum of the weight of 2 atoms of hydrogen 
(2 x 1) and of 1 atom of oxygen, 16. The molecular 
weight of ammonia is 14 (the atomic weight of nitrogen) 
+ 3 f the weight of three atoms of hydrogen) = 17. 

Query. What is the molecular weight of hydrochloric acid ? of nitric 
acid? 

157. Avogaclro's Hypothesis. — If the atomic weights 
of all the elements were known to us there would be little 
difficulty in determining the molecular formulae of com- 
pounds. Thus, if we knew that the atomic weight of 
oxygen is 16, and on analysis found that water consists of 
hydrogen and oxygen in the proportion of 1 part of hydro- 
gen to 8 of oxygen, the simplest formula which we could 
give to the compound would be H 2 0, and we might 
assume that this represents the molecule. A molecular 
formula, according to this, would be nothing more than 
the simplest formula which could be used to express the 
composition of a body, assuming the correctness of the 
commonly accepted atomic weights. In reality, the molec- 
ular formulae mean more than this; they are dependent 
upon a very ingenious and valuable hypothesis, known as 
the hypothesis of Avogadro. 

On comparing the specific gravities of a number of 
gaseous compounds with the molecular weights of the 
same compounds, it is found that the two sets of figures 
bear the same relation to each other. In other words, the 
specific gravity of any compound gas is to the molecular 
weight of the compound, as the specific gravity of any 
other gas is to its molecular weight. This leads to the 



MOLECULES. 



151 



conclusion that equal volumes of bodies in the form of gas 
or vapor contain the tame number of molecules, and this is 
Avogadro's hypothesis. According to the hypothesis, if 
a cubic inch of hydrochloric acid gas contains (say) 1000 
molecules, a cubic inch of any other gas or vapor, 
measured under the same conditions of pressure and 
temperature, also contains 1000 molecules. We can not 
determine the absolute number of molecules present :;i 
airy given volume, and hence, of course, can not determine 
the absolute weight of the molecules; but accepting the 
hypothesis we can easily determine the relative weights 
of molecules of all substances which are gaseous or can be 
converted into vapor. These relative weights compared 
to some standard are what we know as the molecular 
weights. 

We may take any simple molecule, as hydrochloric 
acid, as a standard. The simplest formula which can be 
assigned to this substance to express its composition is 
HC1, in which the atomic weight of chlorine is assumed 
to be 35.5. The molecular weight of a compound of this 
formula is 36.5. Let this be the standard molecule. The 
problem now is to determine the weights of the molecules 
of other bodies in terms of this standard, and in accordance 
with the principle laid down in Avogadro's hypothesis. 
We simply determine the relative weights of equal vol- 
umes of hydrochloric acid and the other gases or vapors, 
and, knowing that the molecular weights bear to one 
another the same relation as these relative weights, the 
molecular weights can easily be deduced. 

The figures which express the relative weights of equal 
volumes of bodies are called the specific gravities. We 
have then only to compare the specific gravities of gases 



152 MOLECULES. 

with that of hydrochloric acid to know the molecular 
weights of these bodies. 

If S' is the specific gravity of hydrochloric acid, and 
36.5 its molecular weight ; S the specific gravity of some 
other gas, and M its molecular weight, we have:- — 

S':36.5::S:M, 

but S ; is known. It is 1.247. Hence we have: — 

1,247 : 36.5 : : S (the sp. gr.of any gas) : M (its molecular wt.). 

In other words, the relation between the specific gravity 
of any gas and its molecular weight is represented by a 
constant quantity which is about 28.8, i.e., — 

M = 28.8, or M = 28.8 X S. 

The molecular weights of all bodies which can be con- 
verted into the form of vapor have been determined by 
means of this rule, and the molecular formulae are based 
upon these determinations. 

158. Determination of Atomic Weights by means 
of Avogadro's Hypothesis. — In order to determine 
atomic weights by means of the hypothesis of Avogadro, 
we first determine the molecular weights of all compounds 
which are gaseous or can be converted into vapor. We 
then analyze these same compounds. On now examining 
the results of the analysis, we select the smallest quantity 
of an element which occurs in any of its compounds, as 
its atomic weight. 

The method may be illustrated by taking some of the 
compounds of carbon as examples. 





MOLECULES, 










Molecular 

Wt. Found. 






Constituents. 




Carbon monoxide 


. 27.90 


12 


pan 


ts C; 16 p 


arts 0, 


Carbon dioxide . 


. 44. 1G 


12 


u 


C; 32 


" 


Marsh gas 


. 16. 1 


12 


u 


C; 4 


" II 


Ethylene . 


. 28.0 


24 


u 


C; 4 


" H 


Acetylene 


. 26.0 


24 


i i, 


C- 2 


" H 



153 



The smallest quantity of carbon contained in any of 
these compounds is represented by the figure 12, and 
consequently this is accepted as the atomic weight, unless 
there is some other compound the molecular weight and 
analysis of which lead us to a smaller figure. 

159. Valence. — Having determined the molecular for- 
mulae of chemical compounds, we see that they differ 
markedly from one another. Take, for example, the 
hydrogen compounds of some of the elements thus far 
considered. We have hydrochloric acid represented by 
HC1, water by H 2 0, ammonia by H 3 N, and marsh gas by 
H 4 C. A fundamental difference between these compounds 
is noticed in the number of hydrogen atoms contained in 
each one. In HC1 we have 1 H ; in H 2 0, 2 H ; in H 3 N, 
3 H ; and in H 4 C, 4 H. The atoms of chlorine, oxygen, 
nitrogen, and carbon are thus seen to differ from one 
another in regard to the number of hydrogen atoms which 
they can hold in combination. The power of any atom to 
hold a certain number of the simplest atoms in combina- 
tion is called its valence. This term is also applied to the 
elements. We speak of a univalent element meaning an 
element the atom of which has the power of holding one 
of the simplest atoms in combination. Thus chlorine and 
hydrogen are univalent elements. 

We may measure the valence of any element by any 



154 MOLECULES. 

univalent element with which it will unite. Thus we 
measure the valence of oxygen by hydrogen. It is 
bivalent because its atom unites with two atoms of hydro- 
gen. In the same way we regard nitrogen as trivalent 
because its atom unites with three atoms of hydrogen ; and 
carbon as quadrivalent because its atom unites with four 
atoms of hydrogen. 

Some elements do not unite with hydrogen. In these 
cases we may measure the valence by means of any other 
univalent element, as chlorine. Thus potassium does not 
unite with hydrogen, but it does unite with chlorine, 
forming the compound KC1, which shows that potassium 
is univalent; calcium forms the compound CaCl 2 , which 
shows that calcium is bivalent. The valences of all the 
elements have thus been determined by a study of the 
formulae of their compounds. In many cases one and 
the same element has more than one valence, as shown in 
the two chlorides of phosphorus, PC1 3 and PC1 5 , in the 
first of which phosphorus appears as a trivalent and in the 
second as a quinquivalent element. 

160. Substituting 1 Power and Valence. — We have 
seen that in the formation of salts the hydrogen of the 
acids is replaced by metals. The number of atoms of 
hydrogen which the atom of any metal can replace is 
determined by the valence of the metal. The atom of a 
univalent metal replaces 1 atom of hydrogen, as is shown 
in the formation of potassium nitrate, KN0 3 , from HN0 3 ; 
the atom of a bivalent metal replaces 2 atoms of hydrogen, 
as in the formation of calcium nitrate, Ca(N0 3 ) 2 , from 
HN0 3 , in which case the calcium atom is represented as 
taking the place of two atoms of hydrogen in two mole- 
cules of nitric acid. In barium sulphate, BaS0 4 , one 



EXERCISES IX EQUATIONS. 155 

atom of the bivalent metal barium takes the place of the 
two hydrogen atoms in sulphuric acid H 2 S0 4 . In making 
hydrogen by treating sulphuric acid with zinc, we had 
another illustration of the replacement of the two hydro- 
gen atoms of sulphuric acid by one atom of the bivalent 
metal zinc. Numerous illustrations of the different sub- 
stituting powers of the metals will present themselves 
when the salts come up for consideration. 

Note. It is customary to consider the part of an acid which remains 
in combination with a metal after the hydrogen has been displaced as a 
group of atoms, and when we wish to take this group more than once, as 
above, we write Ca(N0 3 ) 2 and not CaN 2 6 . By so doing the formula 
shows at a glance what acid took part in forming the compound. 

EXERCISES IN EQUATIONS.- USEFUL PROBLEMS. 

1. The equations previously given might with propriety be termed 
rc Atomic Equations/' since they show what we believe takes place at the 
instant dissociation of a compound occurs. 

We may also write " Molecular Equations," showing the state of 
affairs after all reactions are complete. In order to do this we only need, 
in addition to what we have already practised, to represent the molecules 
of the free elements in some appropriate manner, so that the formula for 
the molecule shall show the number of atoms it contains. It is now 
becoming customary to do this by the use of subscript figures ; thus, 2 , 
H 2 , N 2 , P 4 , S 2 , etc., represent the molecule of oxygen, nitrogen, phosphorus, 
etc. Let us now again take up some of the atomic equations already 
given, and rewrite them to represent molecular conditions : — 

K + H 2 = KOH + H, when rewritten gives 2 K + 2 H 2 = 2 KOH + H 2 , 

Zn + H 2 S0 4 = ZnS0 4 + 2 H becomes Zn + H 2 S0 4 = ZnS0 4 + H 2 ; 

2P + 5O = P 2 O 5 becomes2P 4 +l0O 2 =4P 2 O 5 ; 

S + 2 O = S0 2 becomes S 2 + 2 2 = 2 S0 2 . 

By inspecting the equations thus rewritten it becomes apparent that 
molecular equations are somewhat the more complex of the two, and that 
to write them properly requires a knowledge of the molecular formulae of 
the elements. In the compounds, as previously stated, the formula also 
represents the molecule; not so however with the symbols of the elements ; 
and since it is first necessary to determine the vapor density of an element 



156 EXERCISES IN EQUATIONS. 

before we can determine its molecular formula, it is evident that when we 
come to solids not readily volatilized it is manifestly absurd to write such 
a formula as Au 2 , Pt 3 , etc., especially if we agree to represent the mole- 
cules of elements by subscript figures. 
Write in molecular formulae : — 

KCIO3 = KCl + 30; 
Na + H 2 = NaOH+H; 

C + 2 = C0 2 ; 

3Fe + 40 = Fe 3 4 ; 

Zn + = ZnO. 

2. To calculate the weight of a given volume of any gas from its 
molecular weight : — 

Prob 1. How much does l 1 of HC1 gas weigh at 0° q 

Solution. The molecular weight equals 35.5 + 1 = 36.5, and the density 
(with reference to II) equals 3G.5 -f- 2 = 18.25. Now 11 of II at 0° and 
760 mm weighs 0.0896s, and it is evident that the required weight equals 
18.25 X 0.0896. In case the temperature and pressure vary from standard 
conditions the problem may be finished by Art. 87. 

Note. Note that The density of a gas (H= 1) equals one-half its molec- 
ular weight. This follows from the fact that we take the hydrogen 
molecule, H 2 , as 2 ; or the half molecule, II, as unity. 

Prob. 2. How much do 6 1 of chlorine weigh at 15° and 750 mm ? 

Sug. The molecular formula of chlorine is Cl 2 , and its density equals 
2 X 35.5 -f- 2 — 35.5 or the atomic weight of CI. We may here note that 
the density and atomic weights of the gaseous elements are numerically 
equal. 

Prob. 3. Compute the weights of l 1 of the following gases : O, N, 
N 2 0, N 2 3 , NH 3 , H 2 S, S0 2 , C0 2 , CO. 

3. To compute the specific gravity (air= 1) of a gas from, its molecular 
weight. Divide the weight of l 1 of that gas by the weight of l 1 of air, or 
1.293. 

Prob. 4. What is the specific gravity of C0 2 ? H 2 S ? CO ? NH 3 ? 

4. Show that one needs simply to remember the atomic weights of 
the elements to compute: 1. The molecular weight of any gas; 2. Its 
density ; 3. The weight of l 1 . 



CHAPTER XL 

SULPHUR. SELENIUM AND TELLURIUM. THEIR OCCUR- 
RENCE, PREPARATION, TESTS, ETC. 

SULPHUR. 

Symbol, S ff . — Atomic Weight, 32. — Specific Gravity 
(Crystals), 2.05. 

161. Occurrence. — Sulphur occurs native in volcanic 
regions, and in its compounds with other elements it is 
widely distributed. The most plentiful of these com- 
pounds are the sulphides, iron pyrites, FeS 2 , or Fool's 
Gokl; galena, PbS ; cinnabar, HgS ; and the sulphates, 
gypsum, CaSCX + 2 H 2 ; heavy spar, BaS0 4 ; green 
vitriol or ferrous sulphate, FeS0 4 + 7 H 2 0, etc. 

Native sulphur occurs in regular, yellowish, transparent, 
octahedral crystals, and in other forms derived from this 
primary crystal. It is also found in a massive state 
being then known as volcanic sulphur. ♦ 

162. Preparation. — Since sulphur in its various forms 
is a common article of commerce it may readily be pro- 
cured for class purposes. The common roll sulphur or 
brimstone is prepared by distilling the crude ore in large 
earthen-ware retorts, and condensing the vapors in stone- 
ware condensers. More frequently, however, it is ob- 
tained by building up the crude ore in the form of a kiln 



158 SULPHUR. 

or charcoal pit, where the ore is roasted by burning a 
portion of the sulphur as a fuel. The sulphur is melted 
from its accompanying impurities, and runs down into a 
receptacle prepared to receive it at the bottom of the pit. 

It is afterwards purified by distillation, and cast into the 
ordinary rolls or sticks. 

Flowers of Sulphur, also an article of commerce,, are 
obtained by vaporizing a quantity of sulphur and bringing 
the vapor into a cold condenser, where this variety is pro- 
duced in a manner analogous to snow. 

Exp. 110 p. Dissolve 2 g flowers of sulphur in 13 cc of water, 
to which has been added I s slacked lime (prepared by treating 
1 part quicklime with 3 parts water) . The product calcium 
pentasulphide, CaS 5 , is formed. Write the equation. Now 
add to the solution hydrochloric acid, when the liquid turns 
white, very finely divided sulphur being obtained. 

The substance thus prepared is an article of commerce 
known as lac sulphuris or milk of sulphur. 

163. Properties. — Exp. Ill p. Dissolve l g sulphur in 3 g 
carbon bisulphide, CS 2 . Place the solution in a beaker glass, 
and allow it to evaporate, without heat, in the atmosphere. 
Octahedral sulphur crystals will be obtained. Allow these 
crystals to stand for several days, noting from time to time 
any changes that may occur. 

Sulphur crystals occur in no less than thirty different 
forms all derived from the primary octahedron. The 
specific gravity of these primary crystals at 0° is 2.05. 

Exp. 112 t. Melt in an evaporating dish 100 g sulphur and 
heat to 230°, when the molten mass will turn black. Now 
pour into a basin of cold water, and when cold remove and 
examine the product obtained. Leave for several days in the 
water, and occasional!}- observe what changes occur. 



SULPHUR. 159 

The modification of sulphur thus obtained is known as 
plastic sulphur, and at first strongly resembles caoutchouc, 
in that it is elastic ; it soon becomes brittle, however, 
upon standing. The specific gravity of this form is 1.96. 

Exp. 113 t. Melt in a sand crucible a quantity of sulphur 
and allow it to cool slowly. When a crust forms over the 
surface of the molten sulphur make an opening through the 
crust and pour off the liquid portion. Note the peculiar needle- 
shaped crystals attached to the solid crust. 

Queries. How many different forms or modifications of sulphur have 
.you observed' 2 What changes take place in the crystals last obtained 
when they are allowed to stand q 

Sulphur is extensively used in making sulphuric acid 
and in the manufacture of rubber goods. When heated 
at moderate temperatures with crude rubber gum, 2 to 3 
per cent of sulphur is absorbed, and the product obtained 
is firmer and better adapted to some industrial require- 
ments than the pure gum itself. When the temperature is 
raised to a higher degree the substance called vulcanite 
or ebonite is obtainedo 

Query. What developments in the rubber industry are due to Charles 
Goodyear ? 

Exp. 114 p. Dip into powdered sulphur a pine splinter and 
ignite ; note the flame and the odor emitted. What does the 
odor resemble ? The fumes have the formula S0 2 . Write the 
3quation. 

Sulphur is used in the manufacture of matches and is 
burned for bleaching straw goods. Some forms are also 
employed in medicine. 

It is capable of uniting directly with most metals to 
form sulphides. 



160 SULPHUR A^ID HYDROGEN. 

164. Tests for Free Sulphur. — 1. Free sulphur is dis- 
tinguished, if in considerable quantities, by its physical 
properties, and by its flame and the odor of its fumes. 

2. If the quantity be too small to test as in 1, fuse it on 
platinum foil with sodium carbonate, Na 2 C0 3 ; then place 
the fused mass, which is sodium sulphide, Na 2 S, on a bright 
piece of silver, and moisten with a drop of water. If 
free sulphur be present, a black spot of silver sulphide 
will be obtained. 

Caution. The Na 2 C0 3 and charcoal must be free from sulphur; like 
wise the illuminating gas used for the blow-pipe flame. The alcohol lamp 
is best to use for this test. 

Note. Since sulphur blackens silver, egg spoons, mustard spoons, etc. 
are gilt to prevent their tarnishing. Silver ware blackened by sulphur is 
easily brightened by washing in a solution of potassium cyanide, KCy; 
this is better than scouring, since the cyanide does not attack the pure 
silver. How may the black spot obtained in 2 be removed ? 



SULPHUR AND HYDROGEN. 

165. Sulphur and hydrogen form two compounds, viz. : — 

Hydrogen Sulphide, H 2 S, 
Hydrogen Persulphide, H 2 S 2 (?). 

Of these the first alone is of importance to the beginner. 

Hydeogek Sulphide. 

166. Occurrence. — Hydrogen sulphide, commonly 
known as sulphuretted hydrogen, is of wide occurrence, 
both free and combined. The waters of many famous 
" sulphur springs " contain this gas in large quantities. 
It is a product of volcanic action and of the decomposition 
of albuminous substances; thus the peculiar odor of 



SULPHUR AND HYDROGEN. 161 

rotten eggs is partly due to the hydrogen sulphide 
evolved. 

The sulphides, which may be regarded as derived from 
this acid, are found in great abundance, as already 
mentioned. 

167. Preparation. — Exp. Hop. Place in a test-tube a 
small quantity of water, say 10 cc , and add a small piece of 
ferrous sulphide, FeS ; now add l cc of sulphuric acid, and close 
the tube quickly with a perforated cork containing a glass 
U-shaped jet delivery-tube. The gas will soon issue through 
the jet, when it may be ignited. Note the odor, but do not 
allow more gas than is necessary to escape, since it is some- 
what poisonous. The contents of the tube should be poured 
into the sink as soon as a sufficient amount of gas has been 
obtained, but in case a considerable piece of the sulphide re- 
mains this ma}' be saved for further use. 

This is the general method and the one' almost exclus- 
ively employed in laboratory practice for the production 
of hydrogen sulphide. The chemist thus produces it for 
analytical purposes, as will subsequently { be explained. 
It is well to have a gas chamber wherein this gas may be 
produced and wherein the whole contents of the test-tube 
may be retained, since another reagent, ferrous sulphate, 
is thus produced : — 

FeS + H 2 S0 4 = H 2 S + FeS0 4 . 

This latter compound may be separated by crystallization. 
In case large quantities of sulphuretted hydrogen are 
required, a generating flask may be employed instead of a 
test-tube, and the gas may be washed through warm 
water. An aqueous solution in cold water is to be had, 
but the gas itself, freshly generated, is preferable for 
qualitative work. 



162 SULPHUJl AND HYDROGEN. 

Hydrogen sulphide is also formed by the action of some 
of the other acids on the sulphides ; by burning sulphur 
in an atmosphere of hydrogen; by passing hydrogen 
through boiling sulphur, and by heating paraffine with 
sulphur. All these methods are, for various reasons, not 
well adapted for obtaining the gas in practice. 

168. Properties. — Hydrogen sulphide is a colorless, 
inflammable gas, possessing a disagreeable odor somewhat 
resembling rotten eggs. It is condensed, at ordinary tem- 
peratures under a pressure of 17 atmospheres, to a color- 
less liquid which boils at — 61.8° and freezes at — 85°. 
Its specific gravity at 0° is 1.191, and l 1 weighs 1.522 g . 
l cc of water at 0° absorbs about 4.4 CC hydrogen sulphide, 
forming a slightly acid solution. 

Exp. 116 p. Place in several different test-tubes solutions 
of metallic salts, such as copper sulphate, CuS0 4 ; mercuric 
chloride, HgCl 2 ; lead acetate, Pb(C 2 H 3 2 ) 2 , and silver nitrate, 
AgN0 3 . Generate hydrogen sulphide as in Exp. 115, and 
successively place the jet into these solutions, allowing the gas 
to bubble up through them. Precipitates which are respectively 
the sulphides of the different metals will be formed. 

It is thus that the chemist employs hydrogen sulphide 
in analytical operations, and the great utility of this gas 
becomes apparent when it is known that by its aid the 
metals may be separated into groups. In short, it is 
another group reagent (p. 98). The same is true of one 
of its compounds, ammonium sulphide, (NH 4 ) 2 S. 

Sug. Try the effect of H 2 S upon solutions of arsenic, antimony, 
cadmium, copper, and tin. Note the colors of the precipitates. 

Exp. 117 p. Pass sulphuretted hydrogen through nitric acid ; 
aqua regia ; strong hydrochloric acid ; sulphuric acid. Do you 



SULPHUR AND HYDROGEN. 168 

obtain precipitates? If so, collect and burn on a pine splinter. 
Note the odor of the fumes. AVhat is the sediment obtained? 
What effect do stronger acids have upon hydrogen sulphide? 
Make a solution of lead nitrate, Pb(N0 3 ) 2 , and strongly acidify 
with nitro-hydrochloric acid. Now pass hydrogen sulphide. 
Do you obtain lead sulphide ? Why ? 

169. Tests for the Sulphides. — 1. Free hydrogen sul- 
phide in quantity is distinguished by its odor and by its 
blackening effect upon paper moistened with lead acetate, 
Pb(C 2 H 3 2 ) 2 . Also see Exp. 38. 

2. A sulphide, when fused on platinum foil or a bit of 
porcelain, — as a piece of broken evaporating dish, — with 
sodium carbonate, and moistened, produces a black spot 
when placed on a clean piece of silver. 

Queries. How do the sulphides, as EeS, behave with sulphuric acid 1 
What is meant by a test ? 

Note. The salts of easily reducible metals, such as those of lead and 
mercury, must not be fused on platinum, since these metals form with the 
platinum alloys which are fusible at high temperatures. The platinum 
may thus be ruined. In such cases it is necessary to fuse on charcoal or 
porcelain. What disadvantage does this latter process involve ? 

Hydrogen Perstjlphide, H 2 S 2 (?). 

170. Hydrogen persulphide may be prepared by boiling 
(say) l g slacked lime with 16 cc water and 2 g flowers of 
sulphur. The cold clear solution is then poured into 
dilute hydrochloric acid, when the persulphide falls to the 
bottom of the vessel as an oily liquid. 

It has a very disagreeable odor, more pungent than that 
of hydrogen sulphide. It is not important for the be- 
gin ner» 



164 SULPHUR AND OXYGEN. 



SULPHUR AND OXYGEN. 

171. There are two oxides of sulphur deserving special 
mention, viz. : — 

Sulphur Dioxide, S0 2 , 
and Sulphur Trioxide, S0 3 . 

These oxides are respectively the anhydrides of sulphurous 
and sulphuric acids. The manner in which they combine 
with Ji molecule of water is worthy of notice : — 

1. H 2 + S0 2 = H 2 S0 3 ; 

2. H 2 + S0 3 = H 2 S0 4 . 

It will be seen that in either case one molecule of water 
and one molecule of oxide form but one molecule of acid. 
In the case of the oxacids of nitrogen, bromine, chlorine, 
and iodine two molecules of acid were thus formed. 

Two other oxides corresponding to the formulae, S 2 3 
and S 2 7 , are known. 

Sulphur Dioxide, S0 2 . 

172. Occurrence. — This oxide is the gas formed when 
sulphur is burned in the atmosphere. It occurs free in 
volcanic gases, and combined with other elements, as in 
the sulphites or salts of sulphurous acid. 

173. Preparation. — Exp. 118 p. Place in a generating 
flask fitted with a delivery-tube l g very fine copper filings and 
6 CC strong sulphuric acid. Heat until a gas begins to escape. 
Note the odor, and collect by displacement in a large test-tube, 
or small, tall jar. 

Sug. Some other metals when thus treated also yield sulphur dioxide 
Try several, such as iron, mercury, and lead. 



SULPHUR AND OXYGEN. 165 

When sulphur dioxide is thus prepared the reaction 
may be indicated by the equation : — 

Cu + 2 H 2 S0 4 = CuS0 4 + 2 H 2 + S0 2 . 

Notice the difference between this reaction and that which 

takes place when sulphuric acid and zinc are brought 

together. In the latter case the reaction is represented 

thus : — 

Zn + H 2 S0 4 = ZnS0 4 + H 2 . 

Whenever a metal reacts with an acid the first action con- 
sists in the replacement of the hydrogen of the acid by 
the metal. The hydrogen is liberated and a salt is formed. 
In the case of copper and sulphuric acid, however, the 
reaction does not take place at ordinary temperatures, 
and at higher temperatures the hydrogen which is first 
liberated acts upon the sulphuric acid reducing it to 
sulphur dioxide : — 

H 2 S0 4 + H 2 = 2 H 2 + S0 2 . 

A common method of preparing this gas is to burn 
sulphur in the air. Many other methods are also known, 
such as heating sulphur and carbon with sulphuric acid, 
roasting pyrites, etc. 

174. Properties. — Sulphur dioxide gas is easily con- 
densed by passing it through a spiral glass tube surrounded 
by a freezing mixture. It is very soluble in water, l cc of 
which dissolves, at 0°, about 79.8 CC of this gas. Its specific 
gravity is 2.211, and l 1 weighs 2.862 g . It condenses at 
+ 59° under 79 atmospheres and boils at — 8° under 1 
atmosphere. 

Sulphur dioxide is used in great quantities for preparing 
sulphuric acid, in which case it is prepared by burning 
sulphur or iron pyrites in a current of air. 



166 StTLPHUK AND OXYGEN. 

Exp. 119 p. Suspend in a jar of sulphur dioxide a strip of 
moistened unbleached silk ; a moist wheat straw ; a piece of 
white woollen yarn. 

Sulphur dioxide is used for bleaching such goods as 
chlorine would injure. It produces its effects by reduc- 
tion instead of oxidation, as in the case of those bleaching 
reagents previously noticed. It unites with the oxygen 
of water, liberating hydrogen, and this latter gas enters 
into combination with the coloring matter to form color- 
less compounds. 

Queries. How do milliners prepare the sulphur dioxide which they 
use in bleaching straw goods 1 What other substances have been men- 
tioned as reducing agents 1 What is meant by reduction ? 

A solution of sulphur dioxide in water becomes oxidized 
if it comes in contact with air, sulphuric acid being 
formed. It is probable that in the solution sulphurous 
acid, H 2 S0 3 , is present, and that this takes up oxygen, thus 
passing into sulphuric acid. Write the equations. 

Sulphur dioxide is also a good disinfectant, and will 
prevent the decay of meats and vegetables when applied 
for that purpose. It also prevents fermentation. 

175. Tests for Sulphur Dioxide. — 1. Its odor is marked 
and well known, resembling that of burning matches. 

2. Suspend in this gas a strip of paper which has been 
dipped into a solution of starch paste and potassium 
iodate, KI0 3 . Iodine is liberated, and the paper becomes 
blue •- — 

2 KIU 3 + 5 S0 2 + 4 H 2 = 2 HKS0 4 + 3 H 2 SO, + 1 2 . 

Note. The sulphur dioxide must not be present in excess, or the paper 
will be bleached, hydriodic acid being produced. Write the equation. 



THE SULPHUK OXACIDS. 167 

Sulphur Trioxide, S0 3 . 

176. Sulphur trioxide is somewhat difficult of prepara- 
tion and very unstable owing to the eagerness with 
which it unites with water. 

It is prepared for commerce by passing sulphur dioxide 
together with oxygen over finely divided platinum in a 
highly-heated porcelain tube. It may also be prepared 1>\ 
heating strong sulphuric acid with phosphorus pentoxide : 

H 2 SO, + PA = 2 HP0 3 + S0 3 . 

Sulphur trioxide' was formerly supposed to be the true 
sulphuric acid, but as soon as it was separated it proved to 
be a white crystalline solid without action upon the metals 
in absence of moisture. The discovery of this substance 
brought about a marked change in the views held in 
regard to salts and acids, and was one of the many causes 
which have led up to our present conceptions concerning 
chemical reactions and chemical formulae. 

THE SULPHUR OXACIDS, 

177. In this series eight different acids are known, the 
names and formulae of which are shown by the subjoined 
list: — 

Hyposulphurous acid . . . H 2 S0 2 ; 



Sulphurous acid . 
Sulphuric acid . 
Thiosulphuric acid 
Dithionic acid . 
Trithionic acid . 
Tetrathionic acid 
Pentathionic acid 



. H 2 S0 3 ; 
. H 2 SO s ; 
. H 2 S 2 3 ; 

. h 2 s 2 o 6 ; 

H 2 o 3 Oe > 

. h 2 s 4 o 6 ; 
. hm? 

ISTotis. The root " thion " is of Greek derivation, signifying sulphur. 



168 THE SULFHTTIl OXACIDS. 

By inspection, it will be seen that ail these acids are 
dibasic, possessing two atoms of replaceable hydrogen; 
hence, they yield both acid and normal salts, e.g., mono- 
sodium sulphite, HNaS0 3 ; sodium sulphite, Na 2 S0 3 , etc. 

Acids which contain but one replaceable hydrogen atom 
are called monobasic acids; those which contain two re- 
placeable hydrogens are called hibasic acids; those with 
three are called tribasic acids, and those which contain 
four are called tetrabasic acids. Most common acids 
belong to the first two classes. All the acids previously 
considered, excepting carbonic acid, are monobasic ; the 
latter and the sulphur acids are bibasic. The principal 
tribasic acid is phosphoric acid, H 3 P0 4 . There is no 
common tetrabasic acid. 

Sug. Name the salts formed by the sulphur acids and potassium. 
Write their formulae. 

Note. The student who has thus far followed these pages will have 
noted that the rarer acids are chiefly of interest to the scientist, and that 
they are all unstable and somewhat difficult of preparation. His experi- 
ence, moreover, with these unimportant compounds will have served to 
give him a sufficient conception as to the characteristics of the class of 
substances to which they belong. We shall therefore note but three acids 
of this series; viz., sulphurous, sulphuric, and thiosulphuric acids. 



Sulphurous Acid, H 2 S0 3 . 

178. This acid, as previously noted, is formed when 
sulphur dioxide is passed into water. It is an unstable 
acid constantly giving off sulphur dioxide fumes ; but the 
sulphites are a well known class of salts. 

Exp. 120 p. Pass sulphur dioxide gas into a test-tube of 
cold water ; also into a cold solution of sodium or potassium 
hydroxide. What does each tube contain after passing the 



THE SULPHUR OXACIDS. 169 

gas ? Gently evaporate to dryness the contents of the second 
tube, and a salt is obtained. Complete this equation, — 

H 2 + S0 2 + KOH= . . . 

Use the contents of these tubes for the following : — 

179. Tests for Sulphurous Acid and the Sulphites. 

— 1. Free sulphurous acid in quantity is recognizable by 
its odor. 

2. In traces it may be detected by a solution of starch 
paste and potassium iodate, owing to the blue tinge pro- 
duced. It will also blacken a strip of paper moistened 
with silver nitrate. 

3. The sulphites in solution upon addition of a stronger 
acid (HC1, H 2 S0 4 ) remain clear, yielding sulphur dioxide 
fumes. (See Thiosulphuric Acid.) 

4. When barium chloride is added to a solution of a 
sulphite, the white precipitate barium sulphite, BaS0 3 , is 
thrown down. Divide this precipitate in two parts : to 
the first add hydrochloric acid ; it is soluble. To the second 
add nitric acid ; the sulphite is oxidized to barium sulphate, 
BaS0 4 , a white precipitate insoluble in acids. 

Sug. Complete and balance the following equations, and explain the 
principles they illustrate : — - 

5H 2 S0 3 +2KI0 3 = I+HKS0 4 +H 2 S0 4 + . .; 
Na 2 S0 3 + HCl =S0 2 + . . . +NaCl; 
Na 2 so s + BaC1 2 =^ T aCl+ . . .; 
BaS0 3 +HN0 3 =BaS0 4 +H 2 0+ . , . 

Sulphuric Acid, H 2 S0 4 

180. Occurrence. — Although sulphuric acid does not 
occur in nature except in volcanic waters, it is the most 
important acid known to the chemist and to commerce. 



170 



THE SULPHUR OXACIDS. 



Tt lias even been stated that the prosperity of a country- 
may be estimated by the amount of sulphuric acid which 
that country consumes. 

Its salts are very stable and of great value, as, for ex- 
ample, blue vitriol, CuS0 4 + 5 H 2 0, a salt of copper used 
for galvanic batteries and many other purposes : gypsum 
or land plaster, CaS0 4 + 2H 2 0, used by farmers as a manure ; 
green vitriol or ferrous sulphate, FeS0 4 + 7 H 2 0, a well- 
known salt used in the laboratory as a reagent, and also 
used for purifying water-closets, sewers, etc. ; Glauber 
salts, Na 2 S0 4 + 10 H 2 ; Epsom salts, MgS0 4 + 7 H 2 0, and 
the sulphates of the alkaloids used in medicine. 

181. Preparation. — Exp. 121 t. Although the student 
will have this acid upon his table, where he may study its 
properties at his leisure, it might be well to illustrate the inter- 




Fig. IS. 



esting process of its manufacture. The formation of sulphuric 
acid may be beautifully shown by employing the apparatus 
illustrated in Fig. 18. G is a glass globe used as a condensing 
chamber. B is a generator containing copper filings and 



THE SULPHUR OXACIDS. 171 

sulphuric acid for the purpose of producing sulphur dioxide. 
C is a flask containing water for generating steam. A contains 
copper filings and nitric acid for generating nitrogen dioxide 
and nitrogen trioxide. D is used to convey air into the con- 
densing chamber, and is attached to a hand-bellows. E is an 
escape-pipe to allow the waste gases, nitrogen and nitrogen 
dioxide, etc., to be forced out of the chamber. In practice most 
of these gases are utilized, but in this experiment E must be 
placed in a good ventilating draft. When the products of A, 
B, and C begin to fill the condenser, a steady, but gentle, 
current of air from the bellows must be forced through G- until 
the close of the experiment. Sulphuric acid is thus produced, 
and falls to the bottom of the condenser. 

In preparing commercial sulphuric acid the materials 
and principles used vary but slightly from those illustrated 
in the foregoing experiment. The sulphur dioxide is 
prepared by burning sulphur or roasting iron pyrites, 
FeS 2 , in a current of air. The fumes are conducted 
into immense lead-lined chambers where they are mixed 
with air and steam and the higher oxides of nitrogen, as 
N 2 3 and N0 2 ; or at first a little nitric acid formed from 
sodium nitrate and sulphuric acid is used. The steam is 
obtained from a boiler and is blown into the chamber 
through jets stationed at different points. 

The chemical processes involved in the manufacture of 
sulphuric acid are quite complicated. The essential 
features will appear from the following brief description i 
When the sulphur dioxide and nitric acid first come to- 
gether in the presence of steam this reaction takes place : — 

2 HN0 3 + 3 S0 2 + 2 EUO = 3 H 2 S0 4 + 2 NO. 

As will be seen, the nitric acid is reduced to nitric oxide, 
NO, and this is incapable of oxidizing any more sulphur 



172 THE SULPHUR OXACIDS. 

dioxide ; but the oxygen of the air which is present im 
mediately transforms the nitric oxide into nitrogen tetrox- 
ide, N0 2 (NO + O = NO2), and this, in the presence of 
steam, converts a further quantity of sulphur dioxide into 
sulphuric acid, as indicated in this equation : — 

S0 2 + H 2 + N0 2 = H 2 S0 4 + NO, 

and is itself again reduced to nitric oxide. This NO again 
takes up oxygen to form nitrogen tetroxide, which in turn 
oxidizes sulphur dioxide, and so on, indefinitely. Thus, 
theoretically, starting with a small quantity of nitric 
acid, an infinite quantity of sulphur dioxide could be 
converted into sulphuric acid, as, after the nitric oxide, 
NO, is once formed, it simply serves the purpose of trans- 
ferring oxygen from the air to the sulphur dioxide. Prac- 
tically, of course, there is always some loss of the oxides 
of nitrogen, and this loss must be made good by a fresh 
supply in order to make the operation continuous. 

The acid formed in the leaden chambers is a weak acid 
having a specific gravity of 1.55. It is withdrawn into 
large leaden pans, and concentrated until its specific 
gravity reaches 1.71, when it is quickly removed, since 
any further concentration Avould result in the destruction 
of the pan. 

It is further concentrated and purified in glass or plati- 
num stills until its specific gravity becomes 1.84, when it 
Is ready for the market. 

182. Properties. — Commercial sulphuric acid has an 
oily appearance, and was formerly prepared by distilling 
green vitriol or ferrous sulphate : owing to these facts it 
received the name oil of vitriol. 

When exposed to the atmosphere it soon absorbs mois- 



THE SULPHUR OXACIDS. 173 

ture, thereby becoming dilute. In consequence of its 
great hygroscopic power, it is employed under the receiver 
of the air-pump to aid in concentrating aqueous solutions 
of such substances as would not bear heating without 
undergoing decomposition. Pumice stone moistened with 
sulphuric acid is used to dry those gases upon which the 
acid has no action. The pure acid may also be used in a 
wash-bottle. 

Queries. For which gases already considered may it be used ? For 
which ones should it not be used 1 

When sulphuric acid is brought together with water in 
quantities proportional to their molecular weights, the 
hydrate of sulphuric acid, H 2 S0 4 + H 2 0, is formed. 

When this acid mixes with water much heat is evolved. 
In diluting it with water it is best slowly to add the acid 
to the water, and not the water to the acid, otherwise the 
vessel containing the acid may be broken and a serious 
accident ensue. 

Exp. 122. Try the effect of strong sulphuric acid upon a 
splinter of wood ; a bit of cloth ; a lump of sugar. What 
occurs ? 

Sulphuric acid chars vegetable substances by abstracting 
water, or the elements of water, hydrogen and oxj^gen. 

In its industrial uses, sulphuric acid is employed very 
extensively in the manufacture of soda (sodium carbonate, 
Na 2 C0 3 ), artificial fertilizers, nitroglycerine, etc., and in 
the refining of petroleum. 

Query. Ebr what purposes has sulphuric acid thus far been employed 
in the laboratory % 

183. Tests for Sulphuric Acid and the Sulphates. — 

1. Sulphuric acid or a soluble sulphate may be detected by 



174 THE SULPHUR OXACIDS. 

adding to the solution barium chloride, BaCl 2 , when the 
white precipitate, barium sulphate, BaS0 4 , is obtained. 

This precipitate is insoluble in acids. 

2. An insoluble sulphate may be fused on platinum foil 
or a bit of porcelain with sodium carbonate ; the moist- 
ened residue produces no spot on silver. If fused in the 
same way on charcoal a spot will be produced. 

Queries. If a sulplmte, when treated on charcoal with sodium carbon- 
ate, yields sodium sulphide, Xa 2 S, what action upon the acid has occurred ? 
If the black spot on silver be Ag 2 S, what other compound is probably 
formed in the reaction : — 

2 Ag + Na 2 S = Ag 2 S + ..-.« 

(Sug. H and are present in H 2 to unite with Xa.) Write this equation 
in full, and balance. How can you distinguisli a sulphate from a sulphide, 
by fusing, etc. ? 

NordhausejSt, or Fuming Sulphuric Acid, H 2 S 2 7 . 

184. This acid is made by heating dried ferrous sulphate 
which still contains a little moisture. The reaction is 
represented thus : — 

4 FeS0 4 + H 2 = 2 Fe 2 3 + 2 S0 2 + H 2 S 2 7 . 

It may also be made by passing sulphur trioxide, S0 3 , 
into strong sulphuric acid : — 

H 2 S0 4 + S0 3 =H 2 S 2 7 . 

It breaks up readily, forming sulphur trioxide and sul- 
phuric acid. When a vessel containing it is opened, fumes 
of the trioxide escape ; hence it is called fuming sulphuric 
acid. 

Water acts violently upon it, converting it into ordinary 
sulphuric acid : — 

H 2 S 2 7 + H 2 = 2 H 2 S0 4 . 



THE SULPHUR OXACIDS. 175 

The principal uses of this acid are for dissolving indigo 
in the process of dyeing Saxony blue and for manufactur- 
ing the coal-tar colors. 

Query. Since H 2 S 2 7 = H 2 S0 4 + S0 3 , should this acid be regarded as 
a distinct acid or as a solution of S0 3 in H 2 S0 4 ? 

Thiosulphuric Acid, H 2 S 2 3 . 

185. This acid, in a free state, is so unstable that its 
existence is somewhat problematical; but its salts, the 
thiosulphates, are well-known articles of commerce. The 
principal one, sodium thiosulphate, Na. 2 S 2 3 , is used by 
photographers as a solvent for the unchanged silver salts 
in their prints, which are thus "fixed," as the process is 
termed. This salt is formed by fusing sodium sulphite 
with flowers of sulphur, thus : — 

Na 2 S0 3 + S = Na 2 S 2 3 . 
When a thiosulphate in a hot solution is treated with 
hydrochloric acid or sulphuric acid, free sulphur is de- 
posited, and sulphur dioxide fumes evolved, thus : — 
Na 2 S 2 3 + 2 HC1 == 2 NaCl + S + S0 2 + H 2 0. 
Query. How does a sulphite behave with hydrochloric acid % 
Note. This sulphur acid was formerly known as hyposulphurous 
acid, and its salts as hyposulphites ; while the acid of the formula H 2 S0 2 
was called hydrosulphurous acid, and its salts hydrosulphites. Sodium 
thiosulphate is still commonly known to druggists as hyposulphite of 
sodium. 

186. Tests for the Thiosulphates. — 1. With hydro- 
chloric acid their solutions yield a precipitate of sulphur, 
and give off sulphur dioxide fumes. 

2. Barium chloride, when added to a solution of a thio- 
sulphate, yields a white precipitate soluble in hydrochloric 
acid, but leaving a residue of sulphur. 



176 THE SULPHUR OXACIDS. 

187. To distinguish between the Soluble Salts of 
the Sulphur Acids. — The solution may contain a sul- 
phide, a sulphite, a sulphate, or a thiosulphate. There 
are many ways of making this distinction, one of which is 
as follows : — 

1. Evaporate a portion of the solution to dryness, and 
fuse on charcoal with sodium carbonate, etc. A black 
spot on silver indicates any of these acids. Then fuse on 
porcelain, etc. ; no spot indicates a sulphate, 

2. To a portion of the solution add silver nitrate, 
AgN0 3 : — 

(cl) A black precipitate formed at once indicates a sul- 
phide. 

(J) No precipitate indicates a sulphate. 

(e) A white precipitate, obtained by. adding a single 
drop of the silver nitrate, and which does not dissolve upon 
shaking, indicates a sulphite. This precipitate, upon stand- 
ing, or upon being heated, turns black, metallic silver 
being the final product obtained. 

(d) A white precipitate from a single drop of the nitrate, 
which dissolves upon shaking, indicates a thiosulphate. 
Add an excess of nitrate, and boil. A black precipitate, 
Ag 2 S, is finally obtained. 

(e) If the student is still in doubt as to whether the 
solution contains a sulphite or a thiosulphate, add hydro 
chloric acid to a fresh portion of the solution ; sulphur 
dioxide fumes from a clear solution indicate a sulphite; 
the same fumes from a clouded solution indicate a thio- 
sulphate. 

Sug. Try to distinguish these acids by means of barium chloride,, 
BaCl 2 , etc. 



SULPHUR AND CARBON. 177 

SULPHUR AND CARBON. 

188. Carbon Bisulphide, CS 2 , is a well-known com- 
pound of sulphur and carbon. This is a colorless, inflam- 
mable, highly refracting liquid, boiling at +46°, and 
possessing a specific gravity of 1.292. It lias a powerful 
odor, in its impure commercial forms, and its fumes are 
poisonous ; when pure it has a pleasant, ethereal odor. 

It is prepared by passing the vapor of sulphur through 
a cylinder heated to redness and containing charcoal. 

Carbon bisulphide is employed for a variety of purposes. 
In the laboratory it is used as a solvent for bromine 
and iodine, as we have previously seen ; in the manufac- 
tures it is employed as a solvent for various gums, such as 
rubber gum ; shoemakers mend shoes with a cement made 
by dissolving crude rubber in carbon bisulphide , in woollen 
manufacture it is used to regain the oils with which the 
wool is treated during some of the necessary processes; 
in optics the hollow prisms used for decomposing light, 
and for spectrum analysis, are filled with carbon bisul- 
phide ; in agriculture it is employed as an insecticide, 
and (in the form of salts) in combating the phylloxera. 
It is also said to be of value in exterminating woodchucks 
and other burrowing animals, for which purpose it is placed 
in their burrows, which are then tightly closed with earth. 

The odor of carbon bisulphide betrays its presence, and 
serves as a test. 

SELENIUM. 

Symbol, Se". — Atomic Weight, 79. — Specific Gravity 
(Crystalline), 4.3. 

189. Occurrence. — Selenium is a rare element closely 
resembling sulphur. It was discovered in 1817 by Borzelius 



178 SELENIUM. 

while examining the deposits of the sulphuric acid chambers at 
Gripsholm. It does not occur native, but is found in the 
selenides, such as lead selenicle, PbSe, and the double selenides 
of mercury, lead, silver, and copper. 

190. Preparation. — Owing to the rarity of this element, 
the student will probably do no work with it, therefore general 
processes alone will be briefly given. 

The residue of the sulphuric acid chambers is mixed with 
potassium nitrate and then thrown into a red-hot crucible, where 
it deflagrates, forming potassium selenate, K 2 Se0 4 , which is 
now contaminated with many impurities contained in the 
chamber residue. This impure mass is now digested with 
hydrochloric acid, and the solution filtered and evaporated 
nearly to dryness, selenious acid, H 2 Se0 3 , being formed. This 
acid is then treated with sulphurous acid, thus : — 

H 2 SeO s + 2 H 2 S0 3 = 2 H 2 S0 4 + H 2 + Se. 

The finely divided selenium thus produced is separated by 
filtration. 

191. Properties. — Finely divided selenium when viewed 
by transmitted light has a reddish color. In its properties and 
compounds it resembles sulphur. It is known in three modifi- 
cations ; viz., amorphous, vitreous, and crystalline. Flowers 
of selenium, a scarlet powder, is obtained in a manner similar 
to flowers of sulphur. 

The specific gravity of selenium varies from 4.5 to 4.8. 

192. Selenium Compounds. — 1. Selenium and hydrogen 
form hydrogen selenicle, H 2 Se, a poisonous gas obtained by the 
direct union of the vapor of selenium with hydrogen, or by 
treating potassium selenide with hydrochloric acid. 

2. Selenium and oxygen form selenium dioxide, Se0 2 . when 
the former is burned in a current of the latter, or by treating 
the former with strong nitric acid. 



TELLURIUM. 179 

Seieniuni dioxide and water form selenious acid, H 2 Se0 3 , 
from which the selenites may be derived. Selenium dioxide 
has the odor of rotten cabbage or horseradish. 

3. Selenic acid, H 2 Se0 4 , is obtained by passing a stream of 
chlorine gas through water in which finely divided selenium is 
suspended, thus : — 

Se + 3 Cl 2 + 4 H 2 = 6 HC1 + H 2 Se0 4 . 

This acid forms salts called selenates. 

193. Tests for Selenium and its Compounds. — 1. Free 
selenium burned in the air gives the odor of the dioxide. 

2. Hydrogen selenide is distinguished by its very offensive 
odor. It causes inflammation of the eyes and seriously affects 
the lining membranes of the nose. 

3. The selenides when heated on charcoal give the dioxide 
fumes ; when fused with potassium nitrate, and when the solu- 
tion of the residue in hydrochloric acid is treated with sulphur 
dioxide, they yield free selenium. 

4. The selenites when heated on charcoal also give the fumes 
of burning selenium ; their solutions with sulphur dioxide yield 
free selenium. 

5. The selenates, with sulphur dioxide, yield free selenium 
when acidulated with hydrochloric acid. The fumes of a 
selenate heated on charcoal are also those of the dioxide. 



TELLURIUM. 

Symbol, Te". — Atomic Weight, 125. — Specific 
Gravity, 6.24. 

194. Occurrence. — Tellurium is a rare element which 
occurs native in small quantities and in combination with 
certain metals, as tellurides, particularly with gold, silver, lead, 
and bismuth. 



180 TELLURIUM. 

195. Preparation. — Tellurium is prepared by mixing bis- 
muth telluride (which also contains some sulphur as an im- 
purity) with sodium carbonate and oil ; this mixture is rubbed 
to a paste, placed in a closed crucible, and strongly heated. 
The mass is then lixiviated with water, when a solution of 
sodium telluride and sulphide is obtained. Upon exposure to 
light and air tellurium, in the form of gray powder, is deposited 
in this solution ; this powder is purified by distilling it in an 
atmosphere of hydrogen. 

196. Properties. — Tellurium is a very brittle, bluish- 
white solid, possessing a metallic lustre, and a specific gravity 
of 6.24. It burns in the air with a bluish flame, giving white 
fumes of tellurium dioxide. 

197. Compounds. — 1. Hydrogen telluride, H 2 Te, is a very 

poisonous gas resembling hydrogen sulphide. It is prepared 

thus : — 

ZnTe + 2 HC1 = ZnCl 2 + H 2 Te. 

It burns with a blue flame, is soluble in water, and forms the 
tellurides. 

2. Tellurium dioxide, Te0 2 , is obtained b}^ burning the metal 
in the air or in oxygen. It also occurs native in tellurite. When 
melted it forms a light-yellow liquid. 

3. Tellurous acid, H 2 Te0 3 , is formed by dissolving the metal 
in dilute nitric acid and pouring the liquid into water. 

4. Tellurium trioxide, Te0 3 , is prepared by strongly heating 
telluric acid, thus : — 

H 2 Te0 4 =H 2 + Te0 3 . 

This oxide is an orange-yellow crystalline solid. 

5. Telluric acid, H 2 Te0 4 , is produced by oxidizing tellurium 
with potassium nitrate. 

198. Tests for Tellurium and its Compounds. — 

1. Free tellurium, when dissolved in strong sulphuric acid, 



EXERCISES. 181 

forms a purplish-red solution, from which tellurium may be pre- 
cipitated by adding water. 

2. Tellurium in an)- compound may be detected b}' mixing 
with sodium carbonate and a little charcoal dust, after which it 
is placed in a sealed tube and heated to redness. When cool 
the tube is broken and the contents dissolved in hot water. 
Sodium telluride, Na 2 Te, is dissolved out, coloring the water 
purple. Upon standing, free tellurium is deposited. 

3. Tellurates are first heated to redness, whereby they are 
reduced to tellurites. The tellurites when dissolved in hydro- 
chloric acid and afterwards treated with sulphurous acid yield 
tellurium. 

EXERCISES. 

1. In what experiment did sulphur unite directly with a metal to form a 
sulphide ? In how many ways may a salt be formed ? 

2. What varieties of sulphur may be purchased at the drug store ? 
(Sug. Ask your druggist what varieties he has for sale, and by what 
names they are known.) 

3. Try to obtain sulphur from a piece of vulcanized rubber. 

4. Try to prepare H 2 S from various sulphides that you may find in 
the laboratory. Use H 2 S0 4 , HC1, and HN0 3 . Try "Fool's Gold" or iron 
pyrites. If the acids do not give the desired results, fuse the pyrites on 
charcoal with sodium carbonate and again apply the acids. Do you thus 
obtain H 2 S ? Why ? 

5. The amount of hydrogen sulphide in a solution, as in mineral water, 
may easily be determined by titration. Tor this purpose a standard solu- 
tion of iodine and a fresh solution of starch paste (an indicator) are 
required. The standard solution is prepared thus : — 

Weigh out in a small corked vial (weighing flask) about Is of pure 
iodine; then dissolve about 5s potassium iodide in 20 cc distilled water; 
uncork the vial and immerse it in the iodide solution. When the iodine 
is dissolved, dilute with water so that l cc of the standard solution shall 
contain l m s of free iodine ; preserve this in a perfectly corked bottle in a 
dark place. 

The titration is made thus : To 100 cc of the water to be tested add 
about 2 CC starch paste, and then, in the usual manner, add the standard 
solution of iodine, until a permanent light-blue color is reached. The 



182 EXERCISES. 

number of cubic centimetres standard solution required (N) equals the 

number of milligrams of iodine required to decompose the hydrogen 

sulphide : — 

2I+H 2 S = 2HI + S. 

It is usually safe to deduct from N 1 or 2 m s s to allow for the iodine 
required to color the starch paste, although this is best determined by 
trial. (As soon as the H 2 S is decomposed, upon what does the I act 1 * 
What causes the blue color' 2 ) 

The computation is made thus : — 

254 : N : : 34 : x = wt. of H 2 S in 100 cc - 

In case the amount of H 2 S per litre is required, it = 10 x. Why * How 
obtain the number of cubic centimetres of H 2 S gas per litre ? Whence 
come the numbers, 254 and 34 ? How compute the number of cubic inches 
of H 2 S per U.S. gallon « 

6. Coal containing much sulphides is not adapted to reducing iron 
from its ores. Why 2 Sometimes the sulphides are oxidized to sulphates, 
which are not so objectionable, by piling coal in heaps exposed to the air : — 

FeS 2 +^0= . . .1 

7. Try to obtain a sulphate by treating sulphur or a sulphide with a 
mixture of KC10 3 and HN0 3 . Test for the sulphate with BaCl 2 . 

8. Sulphuric acid or a sulphate is determined quantitatively, thus • To 
(say) 50 cc of the solution containing a sulphate (e.g., K 2 S0 4 ) add hydrochloric 
acid and boil ; while hot add an excess of barium chloride and thoroughly 
agitate : — 

BaCl 2 + K 2 S0 4 = BaS0 4 + 2 KC1. 

Now filter out the BaS0 4 and thoroughly wash with much hot water; the 
ash of the filter-paper used should be known; the precipitate and filter- 
paper are now carefully dried and the precipitate carefully transferred (as 
completely as possible) to a weighed porcelain crucible; the filter-paper is 
now burned and its ash placed within the crucible, which is then heated to 
redness; when the crucible is cool its weight (W) is determined: — 

W — wt. of cruc. — wt. of filter-ash = wt. of BaS0 4 . 

Sometimes the chemist estimates the anhydride of an oxacid. How 
much S0 3 in 17.241s BaS0 4 ? With how much potassa, K 2 0, will this 
amount of S0 3 unite, and how much K 2 S0 4 will it yield ? 

9. The salts of many acids are decomposed and their acids set free by 
sulphuric acid. Why ? 



EXERCISES. 183 

Complete arid balance these equations: — 

KN0 3 + H 2 S0 4 = . . . 
NaCl +H 2 S0 4 =: . . . 
Na 2 C0 3 +H 2 S0 4 = . . . 

10= Make a table showing the similarity of the formulae of the oxides 
and acids of S, Se, and Te. 

11. Ax Exercise in Valence. If to the number representing the 
valence of an element we assign a positive or negative sign, we shall find 
that the algebraic sum of these numbers in any stable chemical compound 
always equals zero, — provided we take * — 

1. The number f or H = + 1. 

2. The number for O = — 2. 

3. The number for any metal in combination as + (except As, Sb, 

etc., with H). 

We may utilize these data to determine the valence of an element in 
combination 5 e.g., what is the valence of I in HI0 3 2 

Solution. 3 = 3 x — 2 = —6. H — + 1. Now the question simply 
is, what number must be added to the + 1 to make +6 (or a number which 
added to —6 will give 0). The number required is evidently + 5. Accord- 
ingly we may conclude that I in HI0 3 is a pentad. 

Queries. What is the valence of S in the following compounds : 
H 2 S; H 2 S0 2 ; H 2 S0 3 ; H 2 S0 4 ; H 2 S 2 3 ? 0f C1 *n: H C1; HCIO; HC10 2 , 
HC10 3 ; KC1<V Of Brin: HBr; HBrO; HBr0 3 ; HBr<V Of P, Si, B, 
and N in their compounds ? 

Sug. Read Johnson on Oxidation in Douglas and Prescott's Qualitative 
Analysis, pp. 251-253. 



CHAPTER XII. 

SILICON AND BORON. 

SILICON. 

Symbol, Si iv . — Atomic Weight, 28.4:— Specific 
Gravity, 2.49. 

199. Occurrence.* — Silicon is a very abundant element, 
occurring in combination with oxygen, or with oxygen and 
other elements. Silica, Si0 2 , known under the names 
quartz, sand, agate, etc., is a very widely distributed sub- 
stance, found in every geological formation. 

The silicates, such as feldspar, mica, and certain clays, 
are well-known compounds. Silicon constitutes from 22.8 
to 36.2 per cent of the earth's crust. 

In a free state, it may be prepared in three modifications, 
— amorphous, graphitoidal, and crystalline. 

200. Preparation. — Exp. 123 t. Silicon may be obtained 
by heating in an iron tube potassium hydrofluosilicate, K 2 SiF 6 , 
with metallic sodium or potassium : — 

K 2 SiF 6 + 4 K = 6 KF + Si. 

A violent reaction occurs. When cool the fused mass is 
treated with water to dissolve the potassium fluoride, while the 
silicon remains as a brown amorphous powder. (See Art. 208 
for K 2 SiF 6 .) 

Exp. 124 t. Place in a porcelain crucible a small quantity 
of amorphous silicon. Carefully lute on the cover with a paste 



SILICON AND OXYGEN. J.50 

of wood ashes, and after thoroughly drying heat the crucible, 
gently at first, and finally to redness. The amorphous mass 
contracts, becoming denser, and assuming the form of plates of 
graphite. 

Exp. 125 t. Crystalline silicon is best obtained by the fol- 
lowing method : A mixture of 3 parts dry sodium Irydrofluo- 
silicate, Na 2 SiF 6 , and 1 part sodium cut in pieces, is rapidly 
introduced into a hessian crucible heated to bright redness. 
Then 9 parts well dried granulated zinc are rapidly added ; and 
finally, the whole covered with a layer of dried sodium chloride. 
The crucible is then closed, the fire allowed to go down, and 
the crucible allowed to cool in the furnace. The silicon unclei 
these circumstances metallizes from its solution in moiten 
zinc, and the zinc afterward solidifies, enclosing the crystals of 
silicon. By treating the mass with hydrochloric acid the zinc 
is dissolved and the crystals left behind. 

201. Properties. — Amorphous silicon, as obtained above, 
is inflammable in the air, when strongly heated, producing 
silicon dioxide. The graphitoidal form is not so readily 
inflammable. At a high temperature, and in absence of 
oxygen, silicon can be fused. Hydrochloric acid does not 
dissolve it, but in strong alkalies it is soluble, thus • — 

Si + 2 KOH -f- H 2 = K 2 Si0 3 + 2 H 2 . 

Silicon (and boron) unite with carbon in the electric fur- 
nace to form carbides. Owing to the hardness of these 
carbides, they are useful for polishing purposes. 

SILICON AND OXYGEN. 

Silicon Dioxide, or Silica, Si0 2 . 

202. Occurrence. — Silicon and oxygen form one well- 
known compound, which occurs in many modifications, as: 



186 SILICON AND OXYGEN. 

1. Quartz crystals, glassy hexagonal prisms terminating in 

hexagonal pyramids. 

2. Amethyst, smoky quartz, rose quartz, and chrysoprase, 

colored varieties of quartz. 

3. Quartzite, a sedimentary rock. 

4. Sand and sandstone, fine fragments of quartz more or 

less cemented together. 

5. Honestone or novaculite, a fine-grained quartz rock. 

6. Chalcedony, a mixture of crystalline and non-crystalline 

quartz. 

7. Agate, consisting of layers of crystallized and amorphous 

quartz of various colors. 

8. Flint and chert, a coarse variety of chalcedony. 

9. Opal, a hydrated form of silica. 

10. Various modifications of the above in which one form is 
passing into another. 

203. Preparation. — Silica maybe artificially obtained 
in two forms : as the so-called " soluble silica," and as an 
insoluble powder. 

Exp. 126 p. Melt in a crucible, 6 g each, potassium carbonate 
and sodium carbonate ; then add 3 g pulverized quartz or white 
saud, and heat till the whole is melted. The molten mass is 
now to be poured out and dissolved in dilute hydrochloric acid. 
The solution thus obtained is now placed in a tray (dialyzing) , 
which may be prepared by stretching parchment paper over a 
wooden hoop, say 10 cm in diameter. This tray is now floated 
on a tub of pure water, when the hydrochloric acid and saline 
substances of the solution pass through the parchment into the 
water of the tub, while the soluble silica remains in the tray. 
It will take about four days to effect this separation, and there 
must be much water in the vessel on which the tray is floated, 
or it must be often changed. 



SILICON AND OXYGEN. 187 

Note. This method of separation is called Dialysis, and depends upon 
the fact that crystallizable substances will pass through the parchment, 
while colloid or non-crystallizable substances will not pass through. 

In this manner a colorless, tasteless, limpid solution is 
obtained, which may be concentrated in a generating-flask; 
but if the concentration be carried too far, the solution 
becomes of a jelly-like consistency. 

Though we here speak of having silica in solution, the 
substance dissolved is really a form of silicic acid, probably 
ortho°silicic acid, H 4 Si0 4 . This loses water very readily, 
and is converted into meta-silicic acid, H 2 SiO s , and this, 
when dried, loses more water, and passes into silicon di- 
oxide, Si0 2 . 

Note. The relations between silicon dioxide and silicic acid, H 2 Si0 3 , 
are similar to those existing between carbon dioxide and carbonic acid. 
Student will indicate the points of resemblance. 

Exp. 127 p. Evaporate strictly to dryness (in an evaporat- 
ing-dish) a portion of the solution obtained in the last experi- 
ment. The powder thus obtained is pure silica. Is it now 
soluble in acids ? In alkalies ? 

204. Properties. — Natural crystals of silicon dioxide or 
quartz are of a glassy lustre, and rank 7° in the scale of 
hardness. They present no cleavage, and a conchoidal 
fracture. The specific gravity of quartz is 2.6 ; of tridy- 
mite, another form, it is 2.3. 

All forms of silica are somewhat soluble in alkalies, 
especially when digested under pressure ; consequently 
many waters, such as those of the Hot Springs in Arkan- 
sas, and the geysers of Iceland, contain, in solution, silica, 
which is deposited upon standing. This explains the 
existence of siliceous sedimentary rocks, like quartzite, 
etc., and of the siliceous petrifactions which so frequently 
occur, especially in the rocks of the Cretaceous Period. 



188 THE SILICON OXACIDS. 

Tripoli is the siliceous remains of the shells or valves of 
microscopic plants, — the Diatoms. 

Sandstone is composed of fragments of quartz cemented 
together by deposited silica ; while 

Conglomerates are larger pebbles similarly joined. Arti- 
ficial conglomerate is now used as a building stone. 

The many different colors which quartz assumes are due 
to the fact that soluble silicon compounds readily absorb 
coloring matters. These colors are either destroyed or 
changed upon application of heat. 

Some forms of quartz, owing to their hardness, and sus- 
ceptibility to a high polish, are prized as ornaments. 

Agates are somewhat porous ; when soaked in honey, 
then treated with sulphuric acid, and afterwards polished, 
they exhibit curious and beautiful markings. 

205. Tests for Silicon Dioxide, — The student will soon 
learn to recognize any of the natural forms of silica by 
'their appearance when crystallized, and by their hardness 
and fracture. (Also see tests for Silicates.) 



THE SILICON OXACIDS. 

206. The silicon acids are hardly known in the free 
state, being very unstable like carbonic acid. Notwith- 
standing the instability of the acids of this series, there 
are three well-marked classes of salts which we may fairly 
suppose to be derived from these acids : — 

1. The mono-silicates. 

2. The bi-silicates. 

3. The tri-silicates. 

Wollastonite, CaSi0 3 , and steatite, Mg 3 H 2 (Si0 3 ) 4 , are 



THE SILICON OXACIDS. 189 

examples of the first ; serpentine, Mg 3 Si 2 7 , and ortho 
clase, Al 2 K 2 (Si 3 8 ) 2 , are examples of the second and third. 
Besides these there are known many polymeric forms of 
each of these classes. 

Sug. Read R. and S., Vol. L, p. 573. 

The various forms of silicic acid may be regarded as 

derived from the acid H 4 Si0 4 by abstraction of water in 

different proportions. The simplest case is represented 

thus : — 

H 4 Si0 4 - H 2 = H 2 Si0 3 , 

the salts of the acid thus formed being the monosilicates. 
Then we have : — 

2 H 4 Si0 4 - H 2 = H 6 Si 2 7 , 

from which the bisilicates are derived ; and, finally, 

3 H 4 Si0 4 - 4 H 2 = H 4 Si s 8 , 

from which the trisilicates are derived. 

207. Tests for the Silicates. — Fuse the solid substance 
with sodium carbonate on charcoal ; dissolve the fused 
mass in hydrochloric acid, and evaporate the solution to 
dryness. If a white powder (Si0 2 ), insoluble in hydro- 
chloric acid, and soluble in potassium hydroxide, be 
obtained, silicic acid, or some of its derived forms, is 
present. 

Other Compounds of Silicon. 

208. Silicon may be made to unite with nearly all the 
elements previously considered, but their compounds are 
unimportant. We may mention here that ; — 

1. Silicon hydride, SiH 4 , is a gas prepared by acting 
upon an alloy of magnesium and silicon with very dilute 
hvdrochloric acid, in the absence of air. 



190 BORON. 

If this gas be allowed to escape through water in 
bubbles, each bubble, upon coming in contact with the 
oxygen of the air, ignites spontaneously, forming ring- 
shaped clouds of silicon dioxide. 

2. Silicon fluoride, as we have previously seen, is ob- 
tained by acting upon glass or silicon with hydrofluoric 
acid (Art. 134). 

3. Hydrofluo silicic acid, H 2 SiF 6 , is prepared when silicon 
fluoride is dissolved in water : — 

3 SiF 4 + 4 H 2 = H 4 Si0 4 + 2 H 2 SiF 6 . 

The sodium or potassium salts of this acid may thus be 
prepared : — 

Exp. 128 t. Silicon fluoride is first prepared by treating in 
a generating-flask sand and fluorspar, CaF 2 , with sulphuric 
acid. This gas is led into water, thus forming a solution of 
hydrofluosilicic acid. When potassium or sodium carbonate is 
added to this solution, a precipitate of the sodium or potassium 
salt is obtained. Care must be taken to avoid an excess of the 
alkaline carbonate, as the salts of hydrofluosilicic acid are de- 
composed by alkalies. 

BORON. 

Symbol, B f ". — Atomic Weight, 11. — Specific Gravity 



(Crystals) , 2. 



>'). 



209. Occurrence. — Boron occurs only in combination 
with other elements. The chief compounds are boric 
acid, H 3 B0 3 ; borax, Na 2 B 4 7 + 10 H 2 ; and boracite, 
2 Mg 3 B 8 15 , MgCl 2 . 

210. Preparation. — Boron may be prepared in two 
modifications, viz., amorphous and crystalline. 



BORON. 191 

Exp. 129 t. Amorphous boron, a dark-brown, odorless, 
tasteless powder, may be obtained by heating boron trioxide, 
B 2 3 , with metallic potassium in an iron tube. 

Exp. 130 t. Crystalline or adamantine boron is obtained by 
fusing amorphous boron, in the absence of air, with metallic 
aluminium. 

This modification of boron ranks 9° in the scale of hard 
ness, and its crystals are prisms or monoclinic octahedra. 

211. Boron Compounds. — 1. Boron trioxide, B 2 3 , is 
the only known oxide of boron, and may be obtained by 
heating to redness boric acid, H 3 B0 3 . It is a brittle, glassy 
solid, readily uniting with water to form boric acid. 

Sug. Write the equation. 

2. Boric acid, H 3 B0 3 , occurs dissolved in the waters of 
certain lagoons in Tuscany, and the market is mostly sup- 
plied from that source. In the vicinity of these lagoons 
are volcanic jets of steam, whose heat is used to evaporate 
the water containing the acid, which is thus obtained in 
crystals; its purification is effected by recrystallization 
from a water solution. 

There are in California several dried up lake beds 
containing massive borax, said to be sufficient to supply 
our wants. Here the acid is obtained by treating the 
borax with hydrochloric acid, and dissolving in hot water. 
From this solution boric acid is also obtained by crystal- 
lization. 

Boric acid is soluble in water and in alcohol. It forms 
the borates. 

212. Tests for Boric Acid and the Borates. — 1. When 
in solution, the free acid turns a strip of turmeric paper 



192 EXERCISES. 

brown, and this color is not changed by dilute hydrochloric 
acid, as is the case with the alkalies. 

Note. It is best for the beginner to compare the action of an alkali 
on this paper with the action of boric acid, noting how the hydrochloric 
acid affects the colors. Also dip a piece of turmeric paper in boric acid; 
then moisten with Na 2 C0 3 and note the greenish-black color produced. 

2. When a solid borate is heated on a platinum loop 
in the reducing flame, the flame is tinged green. 

Note. This test is most striking when the solid has first been calcined, 
then dipped in sulphuric acid and heated to expel the acid, and finally 
moistened with glycerine and treated as in 2. 



EXERCISES. 

1. Silicates in solution are estimated quantitatively as follows : The 
solution is acidulated with hydrochloric acid and evaporated strictly to 
dryness, without allowing the temperature to rise sufficiently high to cause 
the silica, Si0 2 , obtained again to unite with any bases present. The 
residue is again treated with hydrochloric acid ; the white insoluble powder 
Si0 2 is next removed by filtration, and in a manner similar to that 
employed in estimating the sulphates directly determined as silica. 

2. Soak bits of agate in honey ; treat with sulphuric acid, and polish 
on a grindstone or emery wheel. The peculiar markings of the agates are 
thus brought out. 

3. Unite the edges of broken bits of glass with the so-called " soluble 
silica " ; allow the mended articles to dry for two days ; then test the 
strength of the silica as a cement. 

4. What is glass 1 Write an essay on the manufacture of glass. 

5. Ask a blacksmith for what purposes he uses borax. Ask him if a 
mixture of salt and sand will answer as well. What is a flux ? 

6. Eor what use does the barber employ borax 1 

7. Does borax soften "hard" water % Try it. 

8. What is the anhydride of boric acid, H 3 B0 3 1 

9. Dissolve a little borax in HC1 ; then to the solution add alcohol. 
Warm and ignite the alcoholic solution of boric acid thus obtained and 
note the characteristic green flame. 

10. The waters of all our streams abound in diatoms Examine some 
under the microscope. 



CHAPTER XIII. 

PHOSPHORUS. — ITS OCCURRENCE, COMPOUNDS, ETC. — 
GENERAL EXAMINATION OF UNKNOWN SUBSTANCES 
FOR ACIDS. 

PHOSPHORUS. 

Symbol, P. — Atomic Weight, 31. — Specific 
Gravity, 1.83. 

213. Occurrence. — Owing to its great affinity for 
oxygen, phosphorus, although widely distributed, never 
occurs in the free state. Its principal compounds are 
with calcium ; as, phosphorite, Ca 3 (P0 4 ) 2 , and apatite, 
3 Ca 3 (P0 4 ) 2 -f CaClF. It also unites with iron to form 
vivianite, Fe 3 (P0 4 ) 2 + 8 H 2 0. It is also found in the 
igneous rocks, from whose disintegration our alluvial soils 
have been produced ; hence every fertile soil must contain 
phosphates. These phosphates are taken up from the soil 
by growing plants, of whose ripened seeds they form an 
essential constituent. Again, animals consume the plant 
and its seeds, and appropriate the phosphates for building 
up the solid or inorganic portion of their bones ; and it is 
from bones that the greater part of our commercial phos- 
phorus is now obtained. Sombre rite, an impure form of 
calcium phosphate, found in the island of Sombrero, is 
another source of commercial phosphorus. 

214. Preparation. — Phosphorus is obtained from the 
ashes of burned bones. As a matter of economy, the bor.es 



194 PHOSPHORUS. 

are not directly burned, but are subjected to a preliminary 
treatment, in order to save some of their other constitu- 
ents. Thus they are either first digested with water, 
under pressure, in closed vessels, in order to extract the 
gelatine ; or they are distilled in closed retorts, the vola- 
tile products (bone oil) being utilized to some extent ; 
while the remaining solid substance, or "bone black" is 
used for clarifying sugar until worthless for that purpose. 
In either case the remaining solid residue of the bones is 
reduced to ashes b}^ burning in the open air. 

Bone ash, which consists largely of calcium phosphate, 
Ca 3 (P0 4 ) 2 , is first treated with sulphuric acid, when an 
acid calcium phosphate, soluble in water, is obtained : — 

Ca 3 (P0 4 ) 2 + 2 H 2 S0 4 = CaH 4 (PQ 4 ) 2 + 2 CaS0 4 . 

This solution of "super-phosphate of lime," as it is usually 
called, is then evaporated to dryness, and afterward heated 
nearly to redness, when calcium meta-phosphate is ob- 
tained: — 

CaH 4 (P0 4 ) 2 = Ca(PQ 3 ) 2 + 2 H 2 0. 

The meta-phosphate is then intimately mixed with fine 
charcoal dust, and heated to redness in earthen crucibles 
placed in tiers inside of a furnace, their necks extending 
outside of the furnace, and dipping under water in a con- 
denser. Only one-half of the phosphorus is thus liber- 
ated and condensed under the water. The phosphorus is 
now removed, melted under water, and purified by strain- 
ing through chamois leather under water, when it is cast 
into the ordinary sticks of commerce. Before it is cast 
into sticks, the phosphorus may be purified by treating 
it with sulphuric acid and potassium dichromate, E^Cr^Oy. 
All the phosphorus contained by the bone ash may be 



PHOSPHORUS. 195 

liberated by mixing the meta-phosphate with sand and 
charcoal dust, after which it is treated as before. The 
reactions are : — 

1. 2 Ca(P0 3 ) 2 + 5 C = Ca 2 P 2 7 + 5 CO + 2 P. 

2. 2 Ca(P0 3 ) 2 + 2 Si0 2 + 10 C = 2 CaSi0 3 + 10 CO + 4 P. 

215. Properties. — Phosphorus is a highly inflammable 
substance, taking fire at low temperatures. When exposed 
to the air it slowly oxidizes, emitting a phosphorescent 
glow, or luminous and evanescent flashes of light. A 
slight blow or scratch is often sufficient to ignite it. It 
burns with great heat, and when in contact with the flesh 
it produces deep and painful wounds; hence great care 
should be exercised in handling it. It should not be taken 
in the hands nor cut in the air, but should be held by a 
pair of forceps, and cut under water. 

Phosphorus should always be stored, for safe keeping, in 
a bottle of water fitted with a good cork to prevent the 
water from evaporating ; the bottle should then be kept in 
a tightly-covered can, and the whole placed in a cool 
place. 

Owing to the low temperature of its ignition, phosphorus 
is employed in tipping the common lucifer match. The 
composition of match-tips varies ; but nearly all the com- 
pounds employed for making tips contain phosphorus, 
sulphur, and potassium nitrate. 

Phosphorus is also used as an ingredient of many ver- 
min " exterminators," but about five-sixths of all the 
phosphorus produced is consumed for making matches. 

The fumes of phosphorus are characteristic, possessing 
poisonous properties, and an odor with a faint resemblance 
to garlic. When taken internally, phosphorus is a virulent 



196 PHOSPHORUS. 

poison; one decigram may produce fatal results. Severe 
pains in the stomach, vomiting of substances with an odor 
of garlic, and even the characteristic fumes emitted with 
the breath, are the symptoms of phosphorus poisoning. 
Turpentine is a proposed antidote. 

Phosphorus is known in three different modifications, 
viz. : — 

1. Ordinary, or waxy phosphorus, the form usually seen 
in sticks. 

2. Crystalline phosphorus, obtained by dissolving the 
common form in carbon bisulphide, and allowing the solu- 
tion to evaporate. 

3. Red, or amorphous phosphorus, obtained when either 
of the other two modifications is heated to 240° in the 
absence of the air. This variety is not so inflammable as the 
ordinary phosphorus, nor does it give off poisonous fumes ; 
hence it is sometimes used by the matchmakers, who thus 
avoid the dreaded effects of phosphorus poisoning. The 
specific gravity of this variety is 2.106. 

All three varieties of phosphorus burn in the air with a 
bright, luminous flame, forming dense white fumes of phos- 
phorus pentoxide. 

Query. Should an excess of phosphorus be employed in experiment 
41, of what variety would the remainder be 1 

216. Tests for Free Phosphorus. — 1. Phosphorus, in 
considerable quantity, may be detected by its physical 
properties and odor. 

2. In minute quantity, as in cases of phosphorus pois 
oning, phosphorus is detected by dissolving in water the 
substance to be tested, after which it is boiled in a gen- 
erating-flask, and the steam is led through a glass con- 
densing-tube into another flask containing cold water. 



PHOSPHOKUS AND HYDROGEN. 197 

Now, if the room be dark, and if phosphorus be present, a 
■phosphorescent glow is noticeable at the point where the 
steam condenses. 



PHOSPHORUS AND HYDROGEN. 

217. Phosphorus and hydrogen form three compounds : — 

1. Gaseous phosphoretted-hydrogen or hydrogen-phosphide, PH 3 . 

2. Liquid phosphoretted-hydrogen or hydrogen-phosphide, PH 2 . 

3. Solid phosphoretted-hydrogen or hj'drogen-phosphide, (P 2 H?). 

Of these we shall consider only the first. 

218. Gaseous Hydrogen Phosphide, or Phosphine, 

PH 3 , is a gas which ignites spontaneously upon coming in 
contact with the oxygen of the air, owing to the presence 
of traces of the liquid compound PH 2 , this latter substance 
being obtained by the same process that yields the former. 
If the tube from which the phosphine escapes be bent 
upward under water, each bubble upon reaching the air 
ignites, forming beautiful ring-shaped clouds of phosphorus 
pentoxide, P 2 5 . In a still atmosphere these clouds have 
a peculiar rotary motion, illustrating what is known- as 
vortex motion. This striking experiment may be exhibited 
thus : — 

Exp. 131 t. In a generating-flask place a strong solution of 
potassium hydroxide, KOH, and add several small pieces of 
stick phosphorus. Now gently warm, and as soon as flames 
begin to appear at the mouth of the flask, insert a cork carry- 
ing a bent delivery-tube. The lower end of this tube is to dip 
under water placed in an open vessel. As each bubble of the 
gas comes into the air, it ignites with a slight report : — 

4 P -f 3 KOH + 3 H 2 = 3 KH 2 P0 2 + PH 3 . 



198 PHOSPHORUS AND OXYGEN. 

It is somewhat safer to put the apparatus together, aud then 
to pass hydrogen through it long enough completely to displace 
the air ; or the air may be expelled by pouring a little ether 
over the solution before warming. During the experiment cur- 
rents of air in the room are to be avoided. Save the contents 
of the generating-flask for work under hypophosphorous acid. 

Queries. What is the object of these last precautions % What other 
gas behaves like PH 3 ? Show how PH 4 Br and PH 4 I are obtained from 
PH 3 , HI, and HBr. Does PH 3 form salts similar to NH 3 ? 

In this experiment liquid hydrogen-phosphide may be 
obtained by passing the gas through a suitable condensing- 
tube, but both this and the solid form are of no impor- 
tance to the beginner. None of the hydrogen phosphides 
possess acid properties. 

Sug. Make a list of the binary acids. Also make a list of the non- 
acid hydrogen compounds of the elements previously considered. Which 
one is alkaline ? 



PHOSPHORUS AND OXYGEN. 

219. There are two common oxides of phosphorus, viz. : — 

1. Phosphorus Trioxide, P 2 3 . 

2. Phosphorus Pentoxide, P 2 5 . 

1. Phosphorus trioxide is formed when phosphorus is 
burned in a limited supply of air. It is a white powder, 
which possesses a garlic odor, and unites with water to 
form phosphorous acid : — 

3 H 2 + P 2 3 = 2 H3PO3. 

2. Phosphorus pentoxide is obtained by burning phos- 
phorus in the open air or in oxygen. It is also a white 
powder, which eagerly unites with hot water to form phos- 
phoric acid : — 

3 H 2 + P 2 5 = 2 H 3 P0 4 . 



THE PHOSPHORUS OXACIDS. 199 

THE PHOSPHORUS OXACIDS. 

220. There are three important acids in this series :-- 

1. Hypophosphorous acid . H 3 P0 2 , 

2. Phosphorous acid . . . H 3 P0 3 , 

3. Phosphoric acid . . . H 3 P0 4 , 

from which are derived : — 

a. Metaphosphoric acid . . HP0 3 , 

b. Pyrophosphoric acid . . H 4 P 2 7 . 

Since the last two acids may be derived from phosphoric 
acid, all three will be treated under one article, after 
the consideration of the first two acids in the series. 

Hypophosphorous Acid, H 3 P0 2 . 

221. Exp. 132 p. In a generating-flask place 10 cc of a 
solution of barium hydroxide, Ba(OH) 2 , and add two or three 
small pieces of phosphorus. Add a little ether and boil until 
the following reaction is completed : — 

3 Ba(OH) 2 + 2 P 4 + 6 H 2 = 3 Ba(H 2 P0 2 ) 2 + 2 PH 3 . 
The remaining solution is now to be filtered, when the barium 
hypophosphite is obtained in clear solution. To this solution 
carefully add dilute sulphuric acid to precipitate the barium, 
when hypophosphorous acid is obtained, thus : — 

Ba(H 2 P0 2 ) 2 + H 2 S0 4 = BaS0 4 + 2 H 3 P0 2 . 

This acid is a colorless liquid, oxidizing to phosphorous 
and phosphoric acids, when standing exposed to the air. 
It is mono-basic, only one atom of its hydrogen being 
displaceable. If Ave represent by M 7 any univalent metal, 
the general formula for a hypophosphite may be repre- 
sented thus: MYH 2 P0 2 ). 

The hypophosphites may be prepared as in Exp. 131 T, 
by boiling phosphorus with an alkali. The principal use 



200 THE PHOSPHORUS OXACIDS. 

of these salts is for medicinal purposes. The acid and its 
salts are strong reducing agents. 

222. Tests for Hypophosphorons Acid and the Hypo- 
phosphites. — 1. The acid or its salts when heated in a 
test-tube yield phosphine, PH 3 . 

2H 3 P0 2 = PH 3 + H 3 P0 4 . 

2. With silver nitrate a solution of the acid or its salts 
gives a white precipitate, which soon changes to brownish- 
black : — 

4 AgN0 3 + H 3 P0 2 + 2 H 2 = 4 HN0 3 + H 3 P0 4 + 4 Ag. 

3. To the solution of this acid or of its salts add an ex- 
cess of cupric sulphate, CuS0 4 , an insoluble hydride of 
copper, CuH, is formed. Boil a short time ; hydrogen is 
liberated and metallic copper is obtained. 

Note. No. 3 distinguishes H 3 P0 2 from H 3 P0 3 o Thus test the latter. 

Sug. Try hypophosphorous acid, or a hypophosphite, with mercuric 
chloride, HgCl 2 . Do you obtain metallic mercury ? In which tests do 
you find examples of reduction ? Write the equations for HgCl 2 and 
CuS0 4 with KH 2 P0 2 . 

Phosphorous Acid, H 3 P0 3 . 

223. This acid may be obtained by passing chlorine gas 
through a layer of melted phosphorus under water. 
Phosphorus trichloride, PC1 3 , is at first formed, and im- 
mediately reacts upon the water, thus : — 

PC1 3 + 3 H 2 = H 3 P0 3 + 3 HC1. 

The hydrochloric acid is expelled by heat. If the addition 
of the chlorine gas does not stop short of saturation, i.e., 
before tha phosphorus has all disappeared, phosphoric acid 
is produced. Indeed, it is difficult thus to obtain phos^ 
phorous acid free from traces of phosphoric acid. 



THE PHOSPHORUS OXACIDS. 201 

Phosphorous acid is generally dibasic, and M' 2 (HP0 3 ) 
may be taken as a general formula for the phosphites, 
although there are some phosphites known in which the 
acid is tribasic, all the hydrogen being displaced. 

224. Tests for Phosphorous Acid or a Phosphite. — 

1. To the solution add a few drops of sulphuric acid, and 
then add potassium permanganate until a purplish tint is 
reached. This color fades slowly in a cold solution, but 
rapidly when heat is applied. 

Sug. Thus try H 3 P0 2 . How does it behave ? Also try H 3 P0 3 with 
CuS0 4 , as you tried H 3 P0 2 . What results * 

2. To the solution add calcium hydroxide, Ca(OH) 2 ; 
a white precipitate is thrown down. 

Sug. Thus try a hypophosphite. Do you obtain a precipitate ? 

Query. How can you distinguish between a phosphite and a hypo- 
phosphite ? 

Phosphobic Acid, H 3 P0 4 . 

225. This acid is also known as orthopliosphoric acid, 
and its salts as the orthophosphates. It may be obtained 
thus : — 

Exp. 133 p. In an evaporating-dish place a small quantity 
of red phosphorus, and add reagent nitric acid (sp. grav. 1.2) ; 
now heat gently, adding more nitric acid, until the phosphorus 
disappears and red fumes cease to come off. The evaporation 
is to be continued until the excess of nitric acid is expelled. 

The acid thus obtained is a thick, syrupy mass, free from 
odor and readily soluble in water ; when allowed to stand, 
rhombic, six-sided crystals are obtained. 

Phosphoric acid is a tribasic acid, forming acid and normal 



202 THE PHOSPHORUS OXACIDS. 

salts, the phosphates. M r 3 P0 4 is a general formula for the 
phosphates. 

Phosphoric acid is used in medicine, and its salts are of 
common occurrence and much used as fertilizers. The 
phosphates are found in the blood and fluids of animals; 
they are excreted from the kidneys as acid phosphate of 
sodium and phosphates of calcium and magnesium. When 
urea in urine decomposes a double salt of ammonium and 
sodium, NaNH 4 HP0 4 , or microcosmic salt is formed. It was 
from this source that, in 1669, Brandt first prepared phos- 
phorus. 

Metaphosphorjc Acid, HP0 3 . 

This acid is formed when orthophosphoric acid is heated 
to 400°. It is the form in which phosphoric acid is com- 
monly met with in the market (glacial phosphoric acid). 
Its formation is illustrated thus : — 

H 3 P0 4 - H 2 = HP0 3 . 
At ordinary temperatures, in solution in water, it is slowly 
changed to orthophosphoric acid ; the change takes place 
rapidly in boiling water. 

Salts of metaphosphoric acid are formed by igniting 
phosphates belonging to the class represented by the 
formula M / H 2 P0 4 as, for example : — 

KH 2 P0 4 - H 2 = KFO3. 

Query. In what process already considered does a transformation 
from an orthophosphate to a metaphosphate take place 1 

Pykophosphoric Acid, H 4 P 2 7 , 

Is formed when orthophosphoric acid is heated at 200- 

300°, until a small specimen neutralized with ammonia 

gives a pure white precipitate with silver nitrate. The 

change is : — _ 

B 2 H 3 P0 4 - H 2 = H 4 P 2 7 . 



THE PHOSPHOKUS OXACIDS. 203 

Its calts are formed by igniting phosphates of the order 

M' 2 HP0 4 , thus: — 

2 K 2 HP0 4 - II 2 = K 4 P 2 7 . 

Query. In what connection have pyrophosphates been mentioned in 
this book ? 

226. Tests for the Phosphates or their Correspond- 
ing- Acids. — 1. To the solution add a few drops of silver 
nitrate, AgN0 3 . 

(a) A light-yellow precipitate, soluble in ammonia, nitric 
acid, and acetic acid, H(C 2 H30 2 ), indicates phosphoric acid 
or its salts. 

(5) A white precipitate, soluble in nitric acid (without 
effervescence) and in ammonia, indicates pyrophosphoric 
acid or its salts. 

(e) A gelatinous ivhite precipitate, soluble in nitric acid, 
indicates metaphosphoric acid or its salts. 

2. We may also distinguish metaphosphoric acid or its 
salts by acidulating its solution with acetic acid and add- 
ing the white of an egg, which immediately coagulates. 

Sug. Try H 3 P0 4 and H 4 P 2 7 with the white of an egg. What results ? 

3. The most delicate test for orthophosphoric acid or its 
salts is made by adding to the acid or to one of its salts 
dissolved in nitric acid an excess of ammonium molybdate, 
(NH 4 ) 2 Mo0 4 ; upon heating, a yellow precipitate of am- 
monium phospho-molybdate is obtained. See App. for 
reagent ammonium molybdate. 

Note. This test is sufficiently delicate to detect even very minute 
traces of phosphoric acid or of the phosphates. 

4. An orthophosphate with ammonium chloride, am- 
monia and magnesium sulphate, gives a crystalline precipi- 
tate of magnesium-ammonium phosphate, MgNH 4 P0 4 . 

Sug. Try the phosphorus oxacids with salts of lead, calcium, barium, 
and mercury. What results ? 



204 EXAMINATION OF UNKNOWN SUBSTANCES. 



EXAMINATION OF UNKNOWN SUBSTANCES FOR 

ACIDS. 

227. We have now learned something about the principal 
inorganic acids. As we have already seen, Art. 79, some 
elements are acid formers, others form bases ; and we may 
now mention that there are still other elements — as, for 
example, chromium and manganese — that are indifferent, 
acting in certain compounds as acids, in other compounds 
as bases. The consideration of the acids of the indifferent 
elements will be deferred for a time. 

It frequently occurs that the chemist, while working, 
comes upon substances entirely unknown to him ; and 
among other things that he is called upon to determine are 
the acids, which form essential constituents of all salts. 
It is true that the substance may not be acid, but, as we 
have previously seen, the salt of any acid yields the test for 
that acid. Thus, KN0 3 gives the test for nitric acid, and 
NaCl the test for hydrochloric acid, etc. Now since there 
are many acids, it is neither best nor profitable to test at 
random for first one acid and then another; some methodi- 
cal plan should be followed. One method of procedure is 
as follows : — 

If the substance be in liquid form and neutral, evaporate 
it to dryness or nearly so, carefully avoiding a high heat, 
which might decompose certain unstable compounds and 
drive off their acids in vapors. If the substance under 
examination be a solid, no preliminary treatment is neces- 
sary. If the substance in solution be acid, it is either a 
free acid or an acid salt ; in this case the solution must be 
directly tested. Thus two cases naturally arise. 

I. Let us suppose that the substance is neutral and a 



EXAMINATION OF UNKNOWN SUBSTANCES. 205 

solid, or, if a neutral solution, that we have evaporated it 
to dryness. Proceed thus : — 

Place a small portion of the substance in a test-tube ; 
add sulphuric acid ; heat it gently, and note the results as 
follows : — 

1. If a rapid effervescence of an odorless, colorless gas 
occur, the substance is probably a carbonate or an oxalate . 
Now turn to the test for Carbonates or Carbonic Acid, 
Art. 152, and try a fresh portion of the substance by all 
the tests there given. 

In case it prove not to be a carbonate, it is, very likely, 
an Oxalate, a salt of the organic oxalic acid, H 2 C 2 4 . 
This acid (in this connection) may be recognized by its 
giving with calcium chloride, CaCl 2 , a white precipitate 
of calcium oxalate, CaC 2 4 , soluble in hydrochloric acid, 
but insoluble in acetic acid. 

2. Slower effervescence of a colorless gas possessing odor, 
(a) The odor of rotten eggs indicates a sulphide. Test 

by Art. 169. 

(6) The odor of burning matches; try for H 2 S0 3 , Art. 179, 
or H 2 S 2 3 , Art. 186. 

(e) Odor of peach blossoms; try for HCy, Art. 155. 

(7Z) Odor of vinegar ; try for acetates, which are the 
salts of acetic acid, HC 2 H 3 0^, thus: Dissolve the original 
substance in water, add ferric chloride. Fe 2 Cl 6 , and boil. A 
red solution of ferric acetate, Fe 2 (C 2 H 3 2 ) 6 , is formed ; the 
color is destroyed by adding hydrochloric acid. 

(#) An irritating odor indicates HC1, Art. 96 ; HX0 3 
Art. 75 ; or HF, Art. 135. 

3. If a gas having a color and an irritating odor be 
liberated, try for HI, Art. 127: HN0 2 , Art. 72; HCIO, 
Art, 104; or HBr, Art. 117. 



206 EXAMINATION OF UNKNOWN SUBSTANCES. 

4. If a sudden explosion occur, try for HC10 3 , Art. 108. 

5. If none of the preceding phenomena occur, try for 
H 2 S0 4 , Art, 183; H 3 P0 4 , Art. 226; H 3 P0 3 , Art. 224; 
H 4 Si0 4 , Art. 207; H 3 B0 3 , Art. 212; HI0 3 , Art. 131 ; or 
HBr0 3 , Art. 121. 

The student should remember that the foregoing data 
are valuable as indications only, and that these indications 
point toward certain acids to which he should refer, and 
which he should try until he is satisfied that he has found 
the right one. 

II. If the solution be an acid one, proceed thus: — - 

1. To a portion of the solution add HC1 ; then add 
BaCl 2 . If a white precipitate be obtained, the acid present 
is H 2 S0 4 , since barium sulphate, BaS0 4 , is the only 
barium salt (except the salt formed with the rare acid 
H 2 SiP 6 ) which is insoluble in hydrochloric acid. 

2. To a fresh portion of the solution add HN0 3 , and 
then AgN0 3 . 

The following acids give a precipitate insoluble in nitric 
acid: HC1; HI; HBr ; H 2 S ; HCy; HCIO ; and the rarer 
acids, hydro-ferro-cyanic acid, H 4 FeCy 6 , and hydro-ferri- 
cyanic acid, H 3 FeCy 6 . For these last two acids, see Iron. 

3. Test in order for the following acids, using each time 
afresh portion of the solution: HN0 3 ; H 2 C0 3 ; H 3 P0 4 ^ 
H 4 SiCV; H 3 B0 3 ; H 2 S 2 3 ; H 2 S0 3 ; HN0 2 ; PI 2 C 2 4 ; 
H(C 2 H 3 2 ) ; HC10 3 . 

If the acid is not discovered by working carefully up to 
this point, it is a rare acid, and the student will be obliged 
to try for all those previously mentioned in the text and 
not mentioned above. It is true that the acid may be 
quite a common one, belonging to the acids of the indiffer- 
ent acid-forming elements, such as chromium, arsenic, cr 
manganese. 



EXERCISES. 207 

111 such a case the student needs farther experience to 
determine the acid. He will find directions under the 
elements just named. 

EXERCISES. 

1. Phosphorus in iron ores, or in coal used in reducing iron ores, makes 
the iron brittle. The presence of phosphorus in coal may be determined 
by testing the ash for phosphates. 

2. Make a list of the commonly occurring acids; also a list of the 
rarer acids previously mentioned. In testing for acids a substance that 
occurs native, would you expect to find rare acids ? 

3. Dissolve the salt of an acid, and test with litmus paper; some salts 
are acid, some are neutral, and some are alkaline. By trying many salts 
and tabulating the results, the student may learn that normal salts may 
belong to any of the three classes. Do any of the acid salts that you 
have tried belong to the last two classes ? 

4 If in an unknown solution KH 3 and HX0 3 be found, what salt is 
present ? If Na and HC1, what salt ? 

5 The student should be assigned many unknown (to him) salts and, 
by reference to the text, he should determine the acids present. In this 
way he will soon know the tests for the common acids. More than one acid 
may be assigned in one solution, provided the acids do not decompose one 
another, or their tests do not interfere. The metals of many metallic 
salts obscure the test for the acids of the salts ; in this case the metals must 
first be removed, as will hereafter be explained. Xa, K, NH^, Ca, Mg, Sr, 
and Ba do not thus interfere. 

6. For an improved method of obtaining phosphorus, see Chemical 
News, Apr. 4, 1879, p. 147. 



CHAPTER XIV. 

THE METALS. 
INTRODUCTION. 

228. The elements have been divided arbitrarily into 
Metals and Kon-metals, but the dividing line is nowhere 
distinctly drawn. Certain elements, such as arsenic, anti- 
mony, and bismuth, stand midway, in regard to their phys- 
ical and chemical properties, between the two proposed 
classes, and may be fairly placed in either ; consequently 
we may justly consider the elements as forming but 
one class with a regular gradation of properties. In view 
of these facts it is impossible to give a strict and valid 
definition of a metal ; but, in general, we may say : — 

Definition. — A metal is an element which possesses a 
peculiar lustre, known as a metallic lustre, especially when 
in a solid or coherent condition, and the higher oxides of 
which only, and then in very few instances, are acid-forming 
compounds. 

Sug. All, or nearly all, of the oxides of the non-metals form acids. 
State a few exceptions. 

Note. Opacity, high specific gravity, and great atomic weight are 
not exclusively characteristic of the metals. 

229. Properties of the Metals. — Some of the metals 
are barely known to exist, while others have been known 
since the highest antiquity, and their properties have been 
thoroughly investigated. 



THE METALS. 



209 



Of the properties of metals we may note the following: — 
(a) Specific G-ravity. — As a rule the specific gravity 
of a metal is greater than unity ; only three — sodium, 
potassium, and lithium — are less than 1.000. Osmium 
(sp. grav. 22.48) is the heaviest metal, while lithium (sp, 
grav. 0.59) is the lightest. (See Art. 25.) 

Queries. With what are solids and liquids compared to determine 
their specific gravities ? Gases ? How is specific gravity determined ? 

(J) Specific Beat. — The specific heat of an element is 
equal to the number of thermal units required to raise 
one kilogram of that element through 1° C. 

The specific heat of any metal is less than unity, and 
varies somewhat according to the temperature at which 
the observation is made. The following observations, 
which were made at 55°, will serve as an illustration: — 



Cd 0.0567 

Zn 0.0955 

Ag 0.0570 

Mn 0.1220 



Co 0.1070 

Ni 0.1080 

Au 0.0324 

Pt 0.0324 



(<?) Atomic Heat. — When the specific heat of any ele- 
ment is multiplied by its atomic weight, a nearly constant 
quantity (about 6.4) is obtained. This product, in the 
case of any element, is termed the atomic heat of that ele- 
ment. Take, for example, gold and zinc : — 

0.0324 (sp.ht. of Au)xl96.5(at.wt.ofAu)=6.4-(at.ht.ofAu). 
0.0955 (sp. ht. of Zn) x 65.0 (at. wt. of Zn) = 6.4 - (at, lit. of Zn) . 

From an inspection of the results thus obtained was 
deduced Dulong and Petit's law, viz. : — 

The specific heat of an element varies inversely as the 
atomic weight of that element. 

This law is but approximately true, but so nearly true 



210 



THE METALS. 



that it is the best method known for selecting the atomic 
weights of some of the rarer metals. The accepted atomic 
weights of indium, cerium, didymium, and lanthanum 
were thus selected. For example, the atomic weight of 
cerium as determined by analysis of its compounds was at 
first assumed to be about 92 or 94, and the formulae of 
its principal oxides were taken as CeO and Ce 3 4 . The 
specific heat of cerium, however, was found to be 0.04479; 
this would make the atomic heat about 4.2 instead of 6.4. 
Accordingly the atomic weight was increased in the ratio 
f, and the same oxides were assigned the formulae Ce 2 O s 
and Ce0 2 . Both hypotheses agree equally well with the 
percentage composition of these oxides. 

Queries. In what different ways are the atomic weights of elements 
determined 1 If Ce = 94, what per cent of is found in CeO and Ce 3 4 ? 
If Ce = 141, w r hat per cent is found in Ce 2 3 and Ce0 2 ? 

(cT) The Conductivity of the metals for heat and elec- 
tricity is greater than that of the non-metals or any of 
the compounds of either. 

(e) The Melting-points of the metals, so far as determined, 
vary from — 39° to -(-1090° C. Iron and cobalt fuse at 
a white heat, platinum and iridium require the intense 
heat of the oxy-hydrogen blow-pipe, while osmium has 
not been fused at all. The determined melting-points of 
a few metals are : — 



Hg - 40° 

G +30° 

K , + 62.5° 

Na , + 95.6° 

Li . . . . . . +180° 

Sn +235° 

Bi +270° 



Tl . . . . + 294° 

Cd + 315° 

Pb + 334° 

Zn + 423° 

Sb + 425° 

Ag +1000° 

Cu +1090° 



It is difficult to measure the temperature required to 



THE METALS. 211 

melt a metal whose fusing-point is higher than that of 
copper. 

(/) The Molecular Heat of the Salts. — The molecular 
heat of a metallic salt usually equals the sum of the atomic 
heats of its constituent elements : e.g., the atomic heat of 
potassium is 6.5, that of bromine is 6.7, while the molecu- 
lar heat of potassium bromide equals 13.2 or 6.5+6.7. 
The observed molecular heat of a salt agrees very closely 
with the theoretical results thus obtained. 

230. Alloys. — Metals mix in definite and in indefinite 
proportions to form alloys, which possess properties both 
like and unlike the properties of the metals composing 
these alloys. These compounds are of great utility. The 
following list gives the composition of some of the princi- 
pal alloys : — 

1. Gold Coin (U.S ), 90 parts gold, 1 part silver and 9 parts copper. 

2. Silver Coin (U.S.), 90 parts silver, 10 parts copper. 

3. Brass, varying proportions of copper and zinc. 

4. Britannia, varying proportions of brass, tin, antimony, and bismuth. 

5. Pewter, 4 parts tin, 1 part lead. 

6. Queen's Metal, 9 parts tin and 1 each of antimony, bismuth, and lead 

7. Solder, lead and tin in varying proportions. 

8. Speculum Metal, 1 part tin, 2 parts copper. 

9. Bell Metal, 18 parts tin, 22 parts copper. 

10. Bronze, tin, copper, and zinc in varying proportions. 
Bronze Coin, 95 parts copper, 4 parts tin, and 1 part zinc. 

11. Type Metal, 1 part tin, 2 parts lead, and 1 part antimony. 

12. German Silver, 5 parts copper, 2 parts nickel, and 2 parts zinc. 

13. Fusible Metal (melting at 93.75°), 1 part each of tin and lead, and 2 of 

bismuth. This is called "Rose's Metal." 
Fusible Metal (melting at 6b°), 8 parts lead, 5 parts bismuth, 4 parts 
tin, and 3 parts cadmium. This is " Wood's Alloy." 
Sug. Name the uses of the alloys. 

231. Amalgams. — Certain metals, such as silver, gold, 
zinc, tin, copper, etc., unite with mercury to form amal- 



212 THE METALS. 

gams. Some of these amalgams are of great value in the 
arts : battery zincs are amalgamated to prevent local cur- 
rents and the needless waste of the zincs; mirrors are 
made by coating glass with a silver amalgam ; articles to 
be electroplated are first slightly amalgamated to prevent 
the plating from peeling ; gold and silver are extracted 
from their ores by amalgamation ; etc. 

Query. What uses does the chemist make of sodium amalgam ? 

Amalgams are made in different ways: — 

(a) By the direct union of the metal with mercury. 

(Exp. 23.) 

(5) By adding metallic mercury to the solution of a 

metallic salt : — 

Exp. 134 p. To a solution of silver nitrate in a test-tube 
add a drop of metallic mercury. Allow the tube to stand some 
time. The splendid crystals formed are silver amalgam. These 
crystals often assume an arborescent form, whence the name, 
arbor Diance. 

(c) By placing a metal in a solution of a salt of 
mercury : — 

Exp. 135 p. Into a solution of a salt of mercury succes- 
sively place bits of different metals, such as copper, iron, and 
zinc. Also try a nickel coin or a two-cent piece. What ones 
are amalgamated? Is the coating permanent? 

Suo. Mercurous nitrate, Hg 2 (N0 3 ) 2 , is a good salt to use for this pur- 
pose. 

General Caution. Do not bring mercury in contact with valuable 
articles, consisting of such metals as gold, silver, etc. Why ? 

232. Classification of the Metals. — Various methods 
of classification have been proposed and followed, such as 
a classification according to those properties which are 



THE METALS. 213 

made use of in the analysis of substances. Prominent 
among these properties are the solubilities of the metallic 
chlorides, sulphides, hydroxides, carbonates, and phosphates 
in various reagents. This method of classification is 
well adapted to the analytical separation and recognition 
of the various metals, while it interferes in no way 
with their proper consideration in other respects. To 
effect this separation in practice various group reagents are 
employed, and five groups are obtained : — 

A. The First Group Metals. 

In the separation of this group hydrochloric acid is the 
reagent employed, and all the metals belonging to the 
group may be precipitated as chlorides. We mean by this 
that any soluble salt containing a first group metal as a 
base gives, upon the addition of hydrochloric acid to 
a solution of that salt, an insoluble chloride. This group 
contains three metals : — 

Lead Pb, 

Silver . . ., . Ag-, 

Mercury . . . Hg" (in mercurous salts only). 

Note. Mercury, as we have already mentioned, gives two series of 
salts, which will be described under Mercury. The mercurous salts alone 
are precipitated by hydrochloric acid. The mercuric salts belong to the 
second group. It is necessary to state here that lead is not completely 
precipitated by hydrochloric acid. 

B. The Second Group Metals. 

The metals of this group are characterized by yielding 
with hydrogen sulphide, H 2 S, metallic sulphides which are 
insoluble in dilute acids. It is customarj^ in analytical 
operations first to acidulate the solution with hydrochloric 
acid, and then to pass the hydrogen sulphide through the 



214 



THE METALS. 



solution in question. If any or all the metals of this group 
are present, the precipitate obtained consists entirely of 
the sulphides of those metals. This group embraces the 
common metals : — 





Arsenic . . 


. . . As, 




Antimony . 


. . Sb, 




Tin .... 


. . . Sn, 




Bismuth 


Bi, 




Copper . . 


. . . Cu, 




Cadmium . 


Cd, 




Mercury . 


Hg" (in mercuric salts); 


and the rarer 


metals : — 




Gold. . . . 


Au 


Rutheniun 


i . Ru 


Osmium . . Os 


Platinum . . 


Pt 


Iridium . 


. . Ir 


Tungsten . . W 


Palladium . . 


Pd 


Rhodium 


. . Rh 


Molybdenum . Mo 



Note. The sulphides of the first group are also insoluble in dilute 
acids and might be obtained in this group , but in the course of analysis it 
is best first to remove with hydrochloric acid the first group metals. 



C. The Third Group Metals. 
The metals of this group are those whose hydroxides 
and sulphides are soluble in dilute acids but insoluble in 
alkaline solutions. Ammonia and ammonium sulphide, 
(NH 4 ) 2 S, are the third group precipitants, and it is cus- 
tomary first to add to the solution under consideration 
ammonium chloride before adding the group reagents. 
This group includes the common metals: — 



Iron . . . 
Chromium 
Aluminum 
Nickel . . 
Cobalt . . 
Manganese 
Zinc . . . 



Fe, 
Cr, 

Al, 
Ni, 
Co, 

Mn, 
Zn; 







THE METALS. 




21 


id the rarer 


metal 


s: — 








Beryllium . . 


Be 


Cerium . . 


. Ce 


Titanium . 


. Ti 


Indium . . 


In 


Didymium . 


. D 


Zirconium . 


. Zr 


Gallium . . 


Ga 


Terbium 


. Tb 


Uranium . 


. Ur 


Yttrium . . 


Yt 


Erbium . . 


. E 


Tantallum . 


. Ta 


Lanthanum . 


La 


Thorium . 


. Th 


Niobium 


. Nb 




Vanadium . . . 




V 





Note. Many metals of this group form no sulphides in the wet waj 
NiS and CoS are very sparingly soluble in cold dilute HC1. 

D. The Foukth Group Metals. 

We cannot isolate this group by means of their sul 

phides, etc., since these salts are soluble in acid and alkaline 

solutions. The metals of this group are separated by 

means of their carbonates which are thrown down by ammo- 

niunt carbonate, (XH 4 ) 2 CO;3, in solutions made alkaline 

with ammonia. The metals belonging to this group 

are : — 

Barium Ba, 

Strontium . . . Sr, 

Calcium .... Ca, 

Magnesium . . Mg". 

Note. The carbonate of magnesium is somewhat soluble in ammonia, 
and completely so in the presence of ammonium chloride; hence in practice 
it is customary first to add ammonia, ammonium chloride, and then am- 
monium carbonate. The magnesium salts are thus retained in solution and 
afterwards precipitated as a phosphate. 

E. The Fifth Geotjp Metals. 
These metals give no precipitates with common reagents 
since their salts are all soluble. This group includes : — 

Potassium . . . K, 
Sodium ISTa, 

Ammonium . . . NH 4 

(known only in salts ; see Ammonia), 

Lithium .... Li; 



216 THE METALS. 

and the rarer metals : — 

Rubidium Rb, 

Caesium Cs. 

In A, B, C, D, and E are outlined the general principles 
which, with a few details to be explained further on, 
enable us to separate the metals into groups. These 
groups may again be taken up and each metal separated 
and identified. It is thus that we may analyze a solu- 
tion containing any or all the metals. It might be well 
here to give a definition of "analysis" as applied in 
chemistry. 

1. Qualitative Analysis is the separation and detection 
of the individual substances in a given compound. 

2. Quantitative Analysis is the determination oi* the 
weight or amount of each substance present in a given 
compound. 

Query. Which analysis must be made first ? Why ? 

233. Salts of the Metals.; — The metals may be said to 
react with all the acids previously mentioned to form salts. 
The relations existing between the acids and the salts are, 
as a rule, simple and easily understood. A metal replaces 
a certain number of hydrogen atoms depending on its 
valence, a univalent metal replacing one hydrogen atom, 
a bivalent metal, two, etc. 

The simplest salts are those which are derived from 
monobasic acids and univalent metals ; as, 

Potassium nitrate . . . KN0 3 , 

Sodium nitrite .... NaN0 2 , 

Potassium chlorate . . KC10 3 , 

Lithium perchlorate . . LiC10 4 , etc., 

in each of which one atom of the metal replaces one atom 



THE METALS. 217 

of hydrogen, forming a normal salt, or one that contains 
no more replaceable hydrogen. 

In the case of bivalent metals and monobasic acids the 
relations are also simple enough, one atom of the metal 
replacing two atoms of hydrogen in two molecules of the 
acid; as, for example: — 

Calcium hypochlorite . . Ca(C10) 2 , 

Barium nitrate .... Ba (N0 3 ) 2 , 

Copper nitrate .... Cu(N0 3 ) 2 , 

Magnesium chlorate . . Mg (C10 3 ) 2 , etc. 

A monobasic acid generally yields but one salt with any 
given metal. A few curious exceptions to this rule will 
be mentioned further on. 

Taking now a bibasic acid, its two hydrogen atoms may 
be replaced, (1) By two univalent atoms of the same 
kind, as in 

Potassium sulphate . . K 2 S0 4 , 
Sodium carbonate . • . Na 2 C0 3 , etc. 

(2) By two univalent atoms of different kinds as in 

Sodium potassium carbonate, NaKC0 3 , 
Sodium ammonium sulphate, Na(NH 4 )S0 4 , etc. 

(3) By one bivalent metal, as in 

Barium sulphate . . . BaS0 4 , 
Zinc carbonate .... ZnC0 3 , 
Copper sulphate . . . CuS0 4 , etc., 

or (4) Only one of the hydrogen atoms may be replaced^ 
thus giving rise to the formation of a substance which is 
called an acid sah, as in 

Mono-potassium carbonate, KHC0 3 , 
Mono-sodium sulphate . NaHS0 4 , etc. 



218 THE METALS. 

The matter becomes more complicated when we have 
cribasic and tetrabasic acids, and trivalent and quadri- 
valent metals to deal with; but still the student should 
carefully trace the relation between the most complex 
acids and their salts. Most acids are either monobasic 
or bibasic, and only a few of those which we commonly 
have to deal with are tribasic. 

Sug. Let the student classify according to their basicity all the acids 
thus far considered. 

We shall learn that most metals which we commonly 
have to deal with are either univalent, bivalent, or 
trivalent. 

A normal salt frequently unites with a hydroxide to 
form a basic salt, e.g., — 

Pb(N0 3 ) 2 + Pb(OH) 2 = 2 Pb | °^. 
Again, water may thus act on a normal salt, e.g., — 
Bi(N0 3 ) 8 + 2 H 2 = Bi } §^ 2 + 2 HN0 3 . 

Basic mercuric sulphate may be supposed to originate 

thus : — 

HgS0 4 + 2 HgO = Hg 3 S0 6 . 

The structures of some basic salts are exceedingly com- 
plex. 

Exercise. Taking as examples of univalent metals, potassium, sodium, 
and ammonium (NHJ ; of bivalent metals, calcium, barium, and strom 
tium ; and of trivalent metals, aluminium and chromium, let the student 
write the formulae of the following named salts : barium hypochlorite, 
calcium nitrate, mono-potassium phosphate, tri-silver phosphate, tri-calcium 
phosphate, aluminium meta-phosphate, barium iodate, chromium sulphate, 
potassium aluminium sulphate, magnesium ammonium phosphate. 

Suo. The teacher should add to this list, practicing the student until 
it is evident that the principles involved are thoroughly understood. 



A NATURAL CLASSIFICATION OF THE ELEMENTS. 219 

A NATURAL CLASSIFICATION OF THE ELEMENTS. 

234. As previously explained, the elements may be 
roughly divided into metals and non-metals. There are 
other characteristics affording methods of classification, 
such as valence, in which the elements may be classed as 
monads, diads, triads, etc. Again, as we have seen, there 
are elements bearing a close resemblance to one another in 
their chemical compounds, properties, etc., such as chlorine, 
bromine, iodine, and fluorine ; or sulphur, selenium, tellu- 
rium, etc. But a true understanding of natural relation- 
ships requires a careful study of all the available properties 
of the elements and their compounds, and cannot be based 
upon any one characteristic alone. 

That property of the elements which can be expressed 
with the greatest certainty and definiteness is the atomic 
iveight. The specific gravity, although varying within 
certain limits, may assist us to compare those elements 
which are solid at ordinary temperatures. Again, w T e may 
use the atomic volume, which is found by dividing the 
atomic weight of an element by its specific gravity ; the 
number thus obtained shows how many cubic centimetres 
of an element are required to weigh as many grams as 
there are units in the atomic weight of that element. 

The following table presents a number of facts in regard 
to the best known and most distinctly characterized ele- 
ments including all those whose atomic weights are less 
than 88. The lists of compounds are made as full as the 
limits of the table allow, no facts being suppressed in the 
interests of any theory. The student of nature will feel 
best satisfied with that arrangement or classification which 
most fully expresses the natural harmonies. Many dis- 
crepancies are still to be expected through our lack of 
knowledge, or our imperfect appreciation of chemical facts. 



220 A NATURAL CLASSIFICATION OF THE ELEMENTS. 







6 


H 


H 




o -*f 


o g 


o >> 


w £ 




•Z Jl 




en +- 


■H fl 




2.£P 


a o 


"o"> 


£ 3 




o "53 


o& 


<u & 


So 




<£' 


<5 




<\> 


H 


1.0 








Li 


7.0 


6.0 


0.59 


11.9 


Be 


9.1 


2.1 


2.07 


4.4 


B 


11.0 


1.9 


2.5 


4.1 


C 


12.0 


1.0 


3.5 


3.4 


N 


14.0 


2.0 


Gas. 







16.0 


2.0 


Gas. 




F 


• 19.1 


3.1 


<i 




Na 


23.0 


3.9 


0.97 


23.7 


Mg 


23.9 


0.9 


1.74 


13.8 


Al 


27.3 


3.4 


2.60 


10.6 


Si 


28.0 


0.7 


2.39 


10.7 


P 


31.0 


3.0 


2.20 


12.8 


s 


32.0 


1.0 


2.05 


16. 


CI 


35.4 


3.4 


Gas. 


26. 


K 


39.0 


3.6 


0.87 


45.4 


Ca 


39.9 


0.9 


1.58 


25.3 


Sc 


44.0 


4.1 


7 


7 


Ti 


48.0 


4.0 


4.? 


12.5? 


V 


51.2 


3.2 


5.5 


9.2 


Cr 


52.4 


1.2 


6.8 


7.65 


Mn 


54.8 


2.4 


7.14 


7.6 


Fe 


55.9 


1.1 


7.86 


7.09 


Ni 


58.0 


2.1 


8.90 


6.31 


Co 


59.0 


1.0 


8.5 


6.82 


Cu 


63.3 


4.3 


8.9 


7.13 


Zn 


64.9 


1.7 


7.2 


9,37 


Ga 


68.0 


3.1 


5.9 


11.5 


As 


74.6 




5.6 


13.1 


Se 


79.0 


4.4 


4.8 


16.5 


Br 


79.7 


0.7 


3.19 


25. 


Rb 


85.2 


5.5 


1.52 


56.3 


Sr 


87.2 


2.0 


2.5 


34.4 


Ag 


107.7 




10.6 


10.2 


I 


126.5 




4.95 


25.6 


Te 


128.0 


1.5 


6.25 


20.4 






H., 



CH 4 
NH 3 
OH 2 
FH 
Na 4 H 2 



SiH 4 
PH 3 

SH 2 
C1H 

K 4 H 2 (?) 



FeH 2 
Cu 9 H, 



AsH., 
SeH 2 
BrH 



IH 
TeH 2 



HA 

Li 2 2 (? 
BeO 
B 2 3 

co 2 
n 2 o 5 

o 3 

NaA 

MgO 

A1A 

Si0 2 

i 3 A 

so 3 

C10 2 

ka 

Ca0 2 
Ti0 2 

v,o 6 

Cr() 3 

Mn,0 7 
Fe 2 3 
Ni 2 3 

CoA 

CuG 2 
ZnO 
Ga 2 3 
As 2 5 
Se0 2 

Rb 2 

Sr0 9 

Ag 2 2 

iA 

Te0 3 



* ° o 

o x o 



Remarks. 



H 2 
Li 2 
BeO 
B 2 3 

CO 
N 2 

9 



Na 2 
MgO 

A1 2 3 

Si0 2 

p 2 o 3 

so 2 

ci 2 o 

K 2 
CaO 

Ti 2 3 (?) 
V 2 
CrO 
MnO 
FeO 
NiO 
CoO 
Cu 4 
ZnO 

As 2 
Se0 2 C?) 

Rb.>0 

SrO 
Ag 4 

T 2 5 
Te0 2 



There is some reason 
for assuming for Be 
the at. wt. of 13.65 
with the oxideBe 2 U 3 . 

Compare Ozone, -p. 31. 



P 2 is suspected to 
exist. 

Perchloric acid, 
HC10 4 , suggests a 
hypothetical anhy- 
dride, C1 2 7 . 



[Se0 3 . 
H 2 Se0 4 suggests 
Bf 2 0, Br 2 5 , and 
Br 2 7 are hypothet- 
ical anhydrides. 

HI0 4 suggests the 
hypothetical anhy- 
dride L0 7 . 



The following table is based on that of a Russian chemist 
named Mendelejeff, but modified in view of suggestions 
from L. Meyer, Huth, and Muir : — 



1 From Huth's Das period ische Gesetz der Atomgewiclite, Frankfurt a. Oder, 1884. 



I. 



A NATURAL CLASSIFICATION OF THE ELEMENTS. 221 

II. III. IV. V. VI. VII. VIII. 



R.O 


RO 


R,0 3 


R0 2 


R 2 5 


R0 3 


R 2 7 








RH 4 


RH 3 


RH 2 


RH 


1 















Nia 



K 

39 

Cu 

63 

Rb 

85 

Ag 

108 

Cs 

133 



s© 






12 



ft 



AJ 



§6 



27 



28 



Ca 

40 

Zn 



Sc 



G 



a 



Ti „ 

48 

Ge 

72.5 



Y 

89 

In 



87 

Cd 



Zr 

90 



112 

Ba 

137 



114 



118 



La 

139 



Ce _ 



140 



170 < ? > incc Yb _ 



173 



Au 

176 



Hg Ti 



200 



204 



178(?) 



Pb L 



Ra - T . 

225 Th 

232 (?) 



14 

P 

31 

V 

51 

As 

75 

Nb 

94 

Sb 

120 

Pr 

140.5 



Er 



Ta 

182 

Bi 

209 



16 

S 

32 

Cr 

52 



Mo 

96 

Te 

127.6 

Nd 

143.6 



167(?) 



w 

184 



19 

CI 

35.5 

M" Fe.Ni, Co 

56 58.6 59 



S » 6 B J Kr 

80 81.3 



lOOi. 



I 

12? 



150(?) 



169 (?) 



190 (?) 



?) Rh, Ru, Pd 

"' tea ir\t - inn 



104 104.5 106 



lr, Os, Pt 

192.5 193 194 



237(?) 



U 



222 A NATURAL CLASSIFICATION OF THE FLEMENTS. 

In this table the elements are arranged in eight vertical columns, rep- 
resenting eight groups ; while successive series are presented in nearly 
horizontal lines. These are made to incline slightly, so that on rolling the 
table Na will immediately succeed F, K will succeed CI, and so on in a spiral 
line. The first eight or twelve elements present very marked individuality 
of character; some of these are typical of natural groups which follow. 
Elements of most distinct basic character are found towards the left ; 
non-metals predominate in the upper and middle parts of Groups V., VI., 
and VII. ; while the lower part of the table is marked by the more indif- 
ferent elements. A double spiral will be traced beyond Si (beginning with 
P and V respectively) and distinguished by heavy-face and light-face type. 

Many familiar relationships can now be traced out ; thus, K, Kb, and Cs 
are more closely related to each other than they are to Li and Na; Ca, Sr, 
and Ba are very closely related in their properties, while Mg resembles these 
elements in some respects and Zn and Cd in others. Very many facts in 
regard to the properties and compounds of the several elements may be 
fixed in the mind by the law of association when studied with the aid of 
this table, while they could only be retained by a severe effort of memory, 
if viewed independently. 

It will be noticed that the first series has but one member ; group VIII. 
is represented in the even series only, beginning with the fourth ; and the 
element of highest atomic weight yet discovered is in the twelfth series, 
group VI. It is necessary to transpose I and Te in the table, in view of 
their properties. The blanks represent the probable position and approxi- 
mate atomic weights of elements not yet discovered or investigated. 
When Mendelejeff published his table (in 1869) he left two blanks which 
have since been filled by Sc and Ga ; and the properties of these elements 
agree very closely with those expressly predicted from the analogies indi- 
cated in the table. The true position of some of the rarer metals (espe- 
cially those of the cerium group) is still uncertain; these are here 
arranged as in Muir's Principles of Chemistry. 

The harmony of nature here exhibited is most impressive. Is it possi- 
ble that the so-called elements are really compounds ? Did the various 
"elements" of the earth and sun once exist as hydrogen, when our solar 
system was a nebula ? 1 And will modern chemists ever revive the famed 
problem of the alchemists, and seek to turn the base metals into gold ? 
Far more precious than gold is the search for truth ; and the more we 
learn of science, the broader becomes our conception of what we know in 
part, and the deeper should be our reverence for the infinite thought of 
the Creator. 

1 See a paper by F. W. Clarke in Popular Science Monthly for Feb. 1876, p. 463. 



A NATURAL CLASSIFICATION OF THE ELEMENTS. 223 



QUERIES. 

1. In column 2, p. 220, how many numbers differ from whole numbers 
by less than 0.1 ? If the numbers are calculated by comparing with 0= 16, 
they approximate still more closely to whole numbers. 

2. In column 3, what differences are greater than 3 ? Which are less 
than 2 ? 

3. In column 4, where do the numbers increase ? Where do they 
diminish 1 Note the same in column 5. 

4. What monads are indicated by the compounds of column 6 ? What 
diads ? Triads ? Tetrads ? 

5. Note the valence indicated by the oxides in the table, or by any 
other compounds that you may know. 

6. Imagine it possible to begin with an atom of hydrogen, and to build 
up an atom of each of the elements by successive additions of matter; can 
you show that the specific gravity of the product would alternately increase 
and diminish 1 What kind of variation is observed in the atomic volumes ? 
In valence ? 

7. At what points of the series are elements of strongly marked non- 
metallic (or electro-negative) character brought into juxtaposition with 
those of strongly marked metallic or electro-positive character ? Is this 
transition marked by a relatively large or small increase of weight ? 

8. Some elements, such as argon, helium, etc., do not seem to fit in 
any place in the classification table. 



CHAPTER XV. 

THE FIRST GROUP METALS. 

The metals of this group are, as previously explained, 
Lead, Silver, and Mercury. They are of great importance, 
and are utilized in manifold ways. 

LEAD. 

Symbol, Pb". — Atomic Weight, 207. — Specific Heat, 0.0315. 
— Melting-Point, 334°. 

235. Occurrence. — Native, or free, metallic lead occurs 
in very small quantities in certain lead-bearing ores and in 
volcanic tufa. The principal source of lead is its sulphide, 
Galena, PbS. This ore is distributed throughout nearly 
every geological period, but the largest deposits in the 
United States are in the Lower Silurian. Nearly every 
ore of lead is argentiferous, i.e., silver-bearing ; and it is 
not uncommon to find lead associated with other metals, 
as copper, tin, zinc, arsenic, antimonj^, molybdenum, tung- 
sten, etc. 

236. Preparation of Metallic Lead. — Exp. 136 p. In 

a test-tube containing a solution of lead acetate, P^CgHgCX)?} 
place a clean strip of metallic zinc. A dark deposit of lead 
soon forms on the zinc. Complete the equation 

Pb(C 2 H 3 2 ) 2 ? +Zn= . . . 
Collect this deposit of lead, place it on charcoal, and cover 



LEAD. 225 

with sodium carbonate ; now heat the mass before the blow- 
pipe (reducing-flame) , when a bead of metallic lead is easily 
obtained. Place this bead on an anvil and strike it a light 
blow with a hammer. Is it easily malleable ? Cut the flattened 
bead with a knife, and scratch it with the finger-nail, carefully 
noting the hardness, lustre, tarnish, etc. 

Exp. 137 p. Take any lead compound or lead ore, such as 
red lead, Pb 3 4 , or galena, PbS ; place it on charcoal, and heat 
it before the reducing-flame. Do. you again obtain a bead? 
Try this bead as before. 

Exp. 138 p. Solder to each terminal of a Grove, Grenet, or 
Bunsen battery (2 cells) a narrow ribbon of platinum foil. 
Place the platinum strips about l cm apart in a beaker-glass 
containing a strong solution of lead acetate. Treat the deposit 
obtained as before. Is this deposit lead? 

Query. What is Electrolysis 1 

Lead is easily reduced from its ores ; in consequence of 
which it has been known since the highest antiquity. In 
the smelting works, where it is prepared from its ores, 
three distinct processes are employed : — 

1. The air reduction process. In this process the ore 
employed is the sulphide, PbS, which is simply roasted in 
a reverberatory furnace until one portion of the sulphide is 
changed to the sulphate, PbS0 4 , and another to the oxide, 
PbO; the heat is then increased, when the unaltered sul- 
phide reacts with the oxide and sulphate thus : — 

(a) 2 PbO + PbS = 3 Pb + S0 2 . 
(&) PbS0 4 + PbS = 2 Pb + 2 S0 2 . 

2. The carbon reduction process. In this process the 
sulphide is mixed with peat, or other carbonaceous mate- 
rial, and reduced in a blast-furnace. The first and second 
processes are adapted to very pure ores only. 



226 LEAD. 

Query. In what experiment did you obtain lead by a combination of 
these two processes ? 

3. The precipitation process is adapted to the prepara- 
tion of lead from impure ores. In this process the ore is 
melted with cast iron or iron slag. A portion of the lead 
is obtained pure, while the remainder, contaminated with 
other metals, is afterwards so treated that all are saved. 

Queries. In how many different ways can you prepare metallic lead ? 
Why is not the zinc process an economical one ? 

237. Properties, Uses, and Compounds of Lead. — 

Lead is a soft, hea\y, malleable metal possessing a high 
lustre, which is best seen on a freshly-cut surface. On 
exposure to the air this surface soon oxidizes, thus: — 

4Pb + 2 = 2Pb 2 0. 

The oxide Pb 2 is a bluish-gray substance which soon 
forms a coating over the exposed surface, and prevents 
further oxidation. 

Exp. 139 p. Draw the dull surface of a bit of lead over 
a clean white paper. Note that the surface of the lead becomes 
bright, and that a black streak is made on the paper. 

Lead is insoluble in pure cold water free from air, but 
water is seldom or never pure ; hence water flowing 
through, or standing in, leaden pipes or vessels is almost 
certain to contain lead salts in solution. Now, since lead 
and its salts affect the system as a virulent, cumulative 
poison, such waters should never be used for drinking or 
cooking purposes. 

Sug. Explain the action of a cumulative poison. 

Exercise. Let the student name all the uses of metallic lead that he 
can call to mind. Also let him name the alloys of lead and their uses. 

A good solvent for load is dilute nitric acid, since the 
nitrate is a very soluble lead salt. The nitrate and 



LEAD. 227 

acetate solutions in water are the best ones to use as wort 
ing solutions. 

THE PRINCIPAL COMPOUNDS OF LEAD ARE: — 

(«) Lead Oxide or Massicot, PbO, a yellow powder. Lith- 
arge is an impure form of lead oxide, containing oxides of 
other metals, as of copper, iron, etc. Both forms are obtained 
by heating lead in the air. Litharge is used in glazing earthen- 
ware, in preparing flint glass, and in the manufacture of Bed 
Lead or Minium, Pb 3 4 . This last is much used as a pigment, 
and in steam-pipe fitting. 

(b) Lead Acetate, or Sugar of Lead, Pb(C 2 H 3 2 ) 2 , is used 
in medicine ; in the laboratory it is a valuable reagent ; in the 
arts it is used with potassium bichromate, K 2 Cr 2 7 , for dyeing. 

Exp. 140 p. Moisten a strip of white cotton cloth in a solu- 
tion of lead acetate, and then moisten it in a solution of potas- 
sium bichromate. What color is the strip dyed ? 

(c) White Lead, 2 to 3 PbC0 3 -f-Pb(OH) 2 , the principal and 
best white paint known. It is prepared ("Dutch method ") by 
placing rolls of sheet lead in earthenware vessels containing 
vinegar or crude acetic acid. These vessels are then piled in 
tiers, layers of manure or spent tan-bark being placed between. 
The whole is then covered with manure, which, b}^ its decompo- 
sition, furnishes sufficient heat to cause the sheet lead and acetic 
acid to react and to form the compound Pb(C 2 H 3 2 ) 2 .2PbO. 
This compound is next decomposed by the carbon-dioxide 
which escapes from the fermenting mass around the vessels. 
In four or five weeks the process is completed. 

In the " French method" white lead is prepared bypassing 
carbon-dioxide through an aqueous solution of litharge in lead 
acetate. 

(d) Galena, PbS, is a dark, shining solid, crystallizing in 
cubes and in other forms belonging to the regular S3 r stem. It 
is the principal ore of lead. 



228 SILVER. 

(e) Lead Chromate, or Chrome Yelloic, PbCr0 4 , is a pig- 
ment obtained by treating a soluble lead salt with potassium 
bichromate, K 2 Cr £ 7 . 

(/) Lead Chloride, PbCl 2 , is important as a precipitate 
met with in the regular course of analysis. It is a crystalline, 
white solid, soluble in hot water. 

Exercise. Precipitate a dilute solution of lead acetate or nitrate with 
K 2 Cr 2 O r Note the color of the precipitate, and try its solubility in HN0 2 
and ammonia. Thus try other precipitants, as HC1, H 2 S0 4 , (XH 4 ) 2 S, 
KOH, and KI, and test the solubility of the precipitates as before. 
Tabulate the results and keep them for future reference. 

238. Tests for Lead. — 1. Metallic lead is recognized by 
its lustre, tarnish, streak, and malleability. (See Exp. 136.) 

Rem. If the student is not sure, he may dissolve a bit of the metal in 
dilute nitric acid, and test by 2. 

2. Lead, in a solution of its salts, is detected by the 
colors of its precipitates : — 

(a) H 2 S gives PbS (black), 

\b) K 2 Cr 2 7 gives PbCr0 4 (yellow), 

(c) (XH 4 ) 2 C0 3 gives PbC0 3 , Pb(OH) 2 (white), 

(d) KI gives Pbl 2 (yellow scales) , 
{e) H 2 S0 4 gives PbSoJ (white) . 

3. Lead in an unknown solid is detected by reduction 
on charcoal with sodium carbonate, and, if farther identi- 
fication be necessary, by 2, after dissolving the bead in 
nitric acid. 

SILVER. 

Symbol, Ag'. — Atomic Weight, 108. — Specific Heat, 0.0570, 
— Melting-Point, 1000°. 

239. Occurrence. — Silver occurs native in considerable 
quantities with native copper deposits, but its chief sources 



SILVER. 229 

are from the lead furnaces, mentioned in Art. 236, and 
from the following ores : Argentite, Ag 2 S ; Ruby Silver, 
Ag 3 SbS 3 ; Silver-Copper Glance, Ag 2 Cu,S 2 ; Horn Silver, 
AgCl; and other compounds containing silver, copper, 
antimony, arsenic, and sulphur in varying proportions. 

240. Preparation of 3Ietallic Silver. — Exp. 141 p. In 

a test-tube containing a solution of silver nitrate place a strip 
of zinc. Fuse the dark-colored deposit on charcoal before the 
blow-pipe. Try the bead as you tried lead. "What differences 
do you find? Thus reduce silver by means of strips of copper 
and iron. "Write the equations and explain the reactions. 
Will mercury thus jueld metallic silver? 

Exp. 142 p. Try to prepare silver by the electrolysis of 
silver nitrate (see Exp. 138). Fuse to a bead on charcoal 
the substance obtained. Does silver tarnish like lead? 

Exp. 143 p. Heat any silver salt, as AgCl, on charcoal be- 
fore the reducing-rlame. Try to oxidize the bead thus obtained, 
by using the oxidizing flame. Can you thus oxidize lead? Can 
j'ou separate silver from lead by the blow-pipe ? 

Exp. 144 p. To a solution of silver nitrate add tartaric acid, 
H 2 C\H 4 6 . and heat. Xote the silver mirror deposited on the 
sides of the test-tube. Is this an instance of oxidation or 
reduction? What then occurs to the acid? 

Exp. 145 p. To a solution of silver nitrate add a little of a 
solution of chloral hydrate, C 2 HC1 3 0. H 2 0. Make the mixture 
faintly alkaline with ammonia, and heat. Is a silver mirror 
again formed on the sides of the test-tube ? 

Queries. In how many ways have you prepared silver? TVould the 
process of reducing silver with zinc be an economical one, provided there 
were no better processes ? Heat the crystals of the Arbor Diana* (Exp. 
134) in an iron spoon. Can you regain the silver, thus separating silver 
from mercury ? 

Silver is reduced from its ores in three different ways. 



230 SILVER. 

(1) by Cupellation, or Oxidation of lead; (2) by Amal- 
gamation; (3) by Solution and Precipitation. 

1. In the lead furnaces metallic silver is obtained to- 
gether with the lead. This alloy of lead and silver, when 
molten, is allowed to cool slowty; when the temperature 
reaches a certain point, most of the lead separates out in 
crystals, which are removed by means of perforated dip- 
pers. In this way an alloy of lead rich in silver is 
obtained. 

Again, in certain localities, where some of the purer 
ores of silver occur, the crude ore is melted with pure 
lead ; thus a similar alloy is obtained. 

The alloy obtained in either case is freed from lead by 
cupellation, i.e., it is strongly heated in bone-ash vessels, 
called cupels, over which a current of air is flowing. At a 
high temperature the lead is oxidized, while the silver is 
not changed; upon completion of the process, metallic 
silver remains in the bottom of the cupel. 

Query. In what experiment were principles of this process employed ? 

2. In the amalgamation process the ore is ground fine 
(sometimes first roasted) and mixed with sodium chloride 
and mercury; copper sulphate is also frequently added. 
In this way a silver amalgam is obtained. The silver is sep- 
arated by distilling off the mercury in iron retorts. The 
mercury is condensed in cool receivers and again employed 
for the same purpose. 

Query. What experiment foreshadows this process ? 

3. Iii the third process the silver ore is first roasted. 
If it contains the sulphides of iron and copper, which is fre- 
quently the case, the silver is oxidized to the sulphate, 
Ag 2 S0 4 , which, by means of water, may be dissolved out 
from the insoluble oxides of copper and iron formed by 



SILVER. 231 

the roasting. From the solution of silver sulphate thus ob- 
tained metallic silver is precipitated by introducing metallic 
iron. 

If the ore does not contain the sulphides of iron and 
copper, sodium chloride is mixed with the ore before 
roasting. Silver chloride is obtained, which is then dis- 
solved in sodium thiosulphate. Silver sulphide is next 
precipitated by adding to the thiosulphate solution sodium 
sulphide. Finally the sulphur is driven off by heating the 
silver sulphide in a muffle furnace. 

Query. What experiment illustrates these principles 1 
Exp. 146 p. To a solution of silver nitrate add ferrous sul- 
phate. Do you obtain a precipitate? Is it silver? 

Queries. Is silver easily reduced from its salts ? What substances 
have been mentioned which are capable of thus reducing silver % Why 
does silver nitrate blacken the skin or other organic materials 1 Will a 
solution of sugar reduce silver ? 

241. Properties, Uses, and Compounds of Silver. — 

Silver is one of the precious metals, and has been known 
and valued since the highest antiquity. It is white, bril- 
liant, and very ductile and malleable. It does not oxidize 
in the air at any temperature, hence its use in coinage and 
jewelry. 

Silver is readily attacked by ozone, chlorine, bromine, 
iodine, phosphorus, sulphur, and sulphuretted hydrogen. 

Queries. Why does silver coin blacken when carried in the pocket 
with matches 1 Why do egg and mustard spoons blacken ? Why drink- 
ing cups used with sulphur waters ? What substance is a good solvent 
for silver sulphide ? Explain its action on blackened silverware. What 
gases from soft-coal grates and from burning illuminating gas blacken 
silver ? 

Exercise. Name all the uses for which silver is employed. 

The best solvent for silver is nitric acid, and silver nitrate 
is the best salt to use in working solutions. 



232 SILVER. 

THE PRINCIPAL COMPOUNDS OF SILVER ARE: — 

(a) Silver Xitrate, AgN0 3 , or Lunar Caustic. This salt is 
prepared by dissolving silver in nitric acid. It is extensively 
used in medicine as an escharotic agent ; in photography ; in 
the laboraton^ as a reagent ; as an indelible ink, etc. Sticks 
of lunar caustic are prepared by fusing the ordinary crystals of 
silver nitrate and casting the fused mass in moulds. 

Exp. 147 p. Moisten a sheet of paper with silver nitrate; 
dry the paper in the dark ; lay upon the prepared paper a fern 
leaf, a skeleton leaf, or a bit of lace. Cover with a sheet of 
glass. Expose the whole to sunlight until the sheet is black- 
ened. Now in the dark treat the paper with a solution of 
sodium thiosulphate, and then wash perfectly clean with pure 
water. Explain the formation of the u print" obtained. Thus 
prepare a print from a lantern- slide or a photographer's nega- 
tive. 

(b) Silver- Plating Solution may be obtained by dissolving 
silver chloride in an excess of potassium cyanide. The prepa- 
ration of this substance is shown by the two equations : — 

1. AgN0 3 + Nad = AgCl -f- NaNQ* 

2. AgCl + 2 KCy = A gCyKCy + KC1. 

This is used as an electro silver-plating solution. See Gore's 
Electro -Metallurgy for full directions for electro-plating. Also 
read R. and S., Vol. II. , Pt. I., pp. 361-65. 

Note. The AgCl is freed from the NaN0 3 by filtration and washing. 
The silver potassium cyanide solution with the potassium chloride may be 
used as a silver electro-plating solution. 

(c) Silver Chloride, AgCl, is important, in that it is a group 
precipitate, obtained by adding hydrochloric acid to a silver salt 
solution. This precipitate is soluble in ammonia* — 

2 AgCl + 3 NH 3 = (NH 3 ) 3 (AgCl) 2 ( ?) . 



MERCURY. 233 

(d) Silver Bromide, AgBr, is used in photography, and may 
be thus prepared : — 

AgN0 3 + KBr = AgBr + KN0 3 . 

In an impure form silver bromide occurs native. 

Exercise. Precipitate a silver nitrate solution with HC1, and test the 
solubility of the precipitate with NH 3 , KCy, I\a 2 S 2 3 , and HN0 3 . Thus 
obtain and try the precipitates with KBr, KI, and KOH or NaOH. Tabu- 
late the results (with colors of precipitates) and preserve them for 
future reference. 

242. Tests for Silver. — 1. Metallic silver is recognized 
by its lustre and other physical properties. 

2. If the student is not sure, he may dissolve a bit of 
the metal in HN0 3 and add HC1. A white precipitate, 
insoluble in HN0 3 , and soluble in ammonia, indicates 
silver. 

3. Unknown solids may be tested on charcoal with the 
blow-pipe. The bead may be examined as in 1 and 2. 

4. Unknown solutions are tested by adding: — 

(a) HC1, etc., as in 2 ■ 
(6) FeS0 4 , as in Exp. 146 ; 

(c) H 2 S gas, which gives a black precipitate, Ag 2 S, solu- 
ble in KCy and strong HN0 3 . 

5. Silver may be separated from lead by using the oxid- 
izing flame of the blow-pipe as in Exp. 143. 

MERCURY. 

Symbol, Hg'»". — Atomic Weight, 200. — Specific Heat, 0.0319. 
— Melting-Point, —40°. — Boiling-Point, 357.25°. 

243. Occurrence. — Metallic mercury occurs usually in 
very minute globules disseminated through its chief ore, 



234 MERCUKY. 

Cinnabar, HgS. Cinnabar occurs in Mexico, California, 
Spain, Bavaria, China, Japan, and other countries. 

244. Preparation. — Exp. 148 p. In a hard glass tube, 
open at both ends, place a small quantity of vermillion or cinna- 
bar, HgS. Hold the tube somewhat slanting in the Bunsen 
flame, and heat strongly. Sulphur dioxide fumes escape from 
the upper end of the tube, while mercury is deposited in the 
tube in the form of a mirror. Write the equation. 

Exp. 149 p. Heat red oxide of mercury, HgO, in a test- 
tube, and explain what takes place. In what connection have 
you thus treated HgO ? 

Exp. 150 p. In a solution of a mercury salt suspend a strip 
of zinc. In what form do you thus obtain mercury? Thus 
proceed with a piece of clean copper wire ; an iron wire. Do 
you obtain mercury in both cases? Compare the precipitate 
obtained by zinc in the mercury salt solution with those pre- 
cipitates obtained in silver and lead salt solutions. 

Exercise. Prepare a table showing the action of copper, zinc, and 
iron upon the salts of the first group metals. 

Query. Can you obtain metallic mercury from its salts by means of 
reducing agents, such as sugar, chloral hydrate, FeS0 4 , SnCl 2 , etc. ? 
Compare by means of a table the results obtained with those obtained 
with lead and silver salts. 

The commercial preparation of mercury is a very simple 
process. Cinnabar is simply heated in a furnace so con- 
structed that a current of air is passed through the highly 
heated ore. The sulphur is oxidized to sulphur dioxide ; 
the mercury is vaporized, and afterwards condensed under 
water in a cooling chamber. 

Queries. Why was the tube in Exp. 148 open at both ends % In the 
next Exp. why could one end of the tube be closed ? Which of these 
experiments illustrates the process for manufacturing mercury 1 



MERCURY. 235 

245. Properties, Uses, and Compounds of Mercury. — 

Metallic mercury is a silver-white liquid, vaporizing slowly 
at all temperatures between its freezing-point and boiling- 
point. Its properties were discovered and discussed by 
the alchemists, and some of its compounds were found to 
possess great medicinal properties. 

Mercury acts as a poison upon the human system, especi- 
ally when in the form of vapor. 

Metallic mercury is used in constructing thermometers, 
barometers, and other instruments used in physical meas- 
urements. Its amalgams are of great value. 

The best solvent for mercury is nitric acid. Solutions of 
mercurous nitrate, HgN0 3 , and mercuric chloride are good 
working solutions. 

THE PRINCIPAL, COMPOUNDS OF MERCURY ARE : 

(a) Cinnabar, HgS, an ore of mercury ; the artificial sul- 
phide is used as a paint (vermillion). 

(b) Bed Oxide of Mercury, HgO, also called Red Precipitate ; 
it is used in medicine. This compound is obtained by heating 
a very intimate mixture of mercury and mercuric nitrate until 
no red fumes are given off. It may also be obtained as an 
orange-yellow powder by adding an excess of sodium or potas- 
sium hydroxides to the solution of a mercuric salt. 

(c) Mercurous Chloride, or Calomel, Hg CI , is used in medi- 
cine. This substance is prepared by subliming an intimate 
mixture of mercuric chloride and mercury. It is also obtained 
when an excess of hydrochloric acid is added to a solution of 
mercurous nitrate. When thus obtained, it is a Group Pre- 
cipitate which turns black with ammonia : — 

2 HgCl + 2 NH 3 = NH 2 Hg 2 Cl + NH 4 C1. 

Mercurous chloride is soluble in nitro-hydrochloric acid. 

(d) Mercuric Chloride, or Corrosive Sublimate, HgCl 2 , is a 



236 MERCURY. 

deadly poison ; it is used in medicine, and in the laboratory as a 
reagent. This substance is prepared by subliming a mixture of 
mercuric sulphate and common salt. 

(e) Mercurous Nitrate, HglSr0 3 , is often sold fraudulently 
as a silver-plating solution. This is to be had by treating an 
excess of metallic mercury with cold, dilute nitric acid. If the 
acid be in excess, mercuric nitrate, Hg(N0 3 ) 2 , is obtained. 

It will be seen that mercury forms two compounds with 
chlorine and two with nitric acid. Were we to examine the 
entire list of the salts of mercury, we should find numer- 
ous other illustrations of this tendency on the part of the 
metal to form two distinct series of derivatives, of which 
the two chlorides and two nitrates mentioned are good 
representatives. The simplest formulae which can be 
assigned to the two chlorides are HgCl and HgCl 2 , and to 
the two nitrates, HgN0 3 and Hg(N0 3 ) 2 . It would appear 
from these formulae that in the simpler compounds, HgCl 
and HgN0 3 , mercury acts as a univalent element ; whereas, 
in the more complicated compounds, HgCl 2 and Hg(N0 3 ) 2 , 
it acts as a bivalent element. Many have thought it 
best, however, that the formulae of the simpler compounds 
should be doubled, becoming Hg 2 Cl 2 and Hg 2 (N0 3 ) 2 ; and 

perhaps in these compounds the two mercury atoms are 

Hg- 
united with each other, as indicated thus, I , forming 
a bivalent group. Hg — 

However this may be, it is more common nowadays to 
write the simpler formulae, and we thus have the two 
series of mercury compounds corresponding to Hg CI and 
HgCl 2 . The former is called mercurous chloride, and the 
latter, mercuric chloride. The chloride containing the 
smaller proportion of the acid constituent is designated by 
the terminal syllable -ous, while that chloride which con- 



MERCURY. 237 

tains the larger proportion of the acid constituent is desig- 
nated by the syllable -ic. The mercurous salts correspond 
in composition to mercurous chloride. The mercuric salts 
correspond to mercuric chloride. 

Similar series of salts are known in connection with : 
iron, which gives ferrous and ferric salts ; copper, which 
gives cuprous and cupric salts ; and many other metals. 
The most marked cases are those of mercury, iron, and 
copper. 

Only the mercurous salts are precipitated in the first 
group. The mercuric salts are thrown down in the second 
group. 

Exercise. With a solution of a mercurous salt try the precipitants 
HC1, H 2 S, KI 3 and KOH. Try the solubility of each precipitate in HX0 3 , 
and in nitro-hydrochloric acid. Thus proceed with a mercuric salt ; make 
a table comparing the results. 

246. Tests for Mercury and the Mercury Compounds 

— 1. Metallic mercury is readily recognized by its physi- 
cal properties. 

2. An unknown solid is tested for mercury by heating 
it in a test-tube with anhydrous sodium carbonate, Na 2 C0 3 . 
A mirror of metallic mercury is formed on the sides of the 
test-tube. 

3. An unknown solution is tested for mercury by add- 
ing:— 

(a) HC1. If a white precipitate be formed, filter it out 
and moisten it on the filter-paper with ammonia. If the 
precipitate turns black, mercury in the mercurous condi- 
tion is present. 

(5) Through the filtrate from (a) pass hydrogen sul- 
phide. Mercury, in the mercuric condition, gives a black 
precipitate, which is to be tested farther by dissolving it 



238 MERCURY. 

in nitro-hydrochloric acid, and evaporate to expel the excess 
of acid; to this solution add stannous chloride, SnCl 2 : — 
HgCl 2 + SnCU = Hg + SnCl 4 . 

The mercury thus obtained appears (usually after some 
time) as a finely-divided, black precipitate. 

4o A copper wire in a solution containing a mercury 
salt is soon coated with a silver-white deposit. 

5. A solid may be dissolved in nitro-hyclrochloric acid, 
and the solution directly tested by SnCl 2 , or by 4. 

247. To separate and identify Lead, Silver, and Mer- 
cury (Hg'). — 1. To a solution containing salts of these 
three metals add HC1 ; the compounds PbCl 2 , AgCl, and 
Hg 2 Cl 2 are thus obtained together in the form of a pre- 
cipitate. Filter and wash this precipitate with a little cold 
water. 

Note. Lead is not completely precipitated by HC1; consequently some 
lead usually passes over into the second group. 

2. Add much hot ivater to the precipitate as it lies on 
the filter-paper. The lead chloride, PbCL, is thus dis- 
solved, and will now run through the filter-paper. Collect 
this solution in a beaker, and test for lead by Art. 238, 2. 

3. The undissolved precipitate on the filter-paper now 
consists of AgCl and Hg 2 Cl 2 . The silver chloride, AgCl, 
may now be dissolved out by adding a little ammonia. 
Collect the solution, (NH 3 ) 3 (AgCl) 2 , as it runs through, 
and test for silver by acidulating it with nitric acid ; AgCl 
is again precipitated : — 

(NH 3 ) 3 (AgCl) 2 + 3 HN0 3 = 2 AgCl + 3 NH 4 N0 3 . 

Note. The formation, in this connection, of the white precipitate, 
AgCl, upon adding nitric acid, is sufficient to identify silver ; but in case 
the precipitate be plentiful, a bead of metallic silver may be had, as in 
Art. 249 3. 



MERCURY. 239 

4. At the same time that the silver chloride dissolves 
in ammonia, the mercurous chloride, Hg CI , turns black 
(245,c) and remains on the filter-paper. This blackening, 
in this connection, is a sufficient indication that mercurous 
compounds are present. A farther test, by 246, 5, may be 
employed, however, if desirable. 

248. To separate Mercury, Lead, and Silver by the 
JBlow-Pipe. — Exp. 151 p. Make an amalgam of silver, as 
in Exp. 134. Also make an amalgam of lead by warming and 
rubbing bits of lead and mercury in an evaporating-dish ; mix 
the two amalgams ; you thus have a compound of metallic 
mercury, lead, and silver. 

1. Carefully heat a bit of Jlis compound on charcoal in the 
reducing -fL&me until you think you have driven off the mercury. 
Dissolve the residue in dilute nitric acid, and test by Art. 247. 
If the separation of the mercury was complete, you will obtain 
tests for lead and silver only. 

2. Heat another bit of the compound on charcoal in the 
oxidizing flame. You may thus drive off the mercury and 
oxidize the lead, leaving a bead of metallic silver. Dissolve 
this bead in nitric acid, and try for silver, lead, and mercury by 
Art. 247. If the separation of mercury and lead was complete, 
you will obtain a test for silver only. 

Note. In case the amalgam, when heated as in 1, spits out and is 
lost, this step may be accomplished by carefully heating and shaking a 
fresh portion in an iron spoon. 

249. Reactions in Group I. — Balance these equations 
What principles do they illustrate ? 

(1) Pb + HN0 3 = Pb(N0 3 ) 2 + NO+H 2 0. 

(2) Ag + HN0 3 = AgNO s + NO + H 2 0. 

(3) Hg 2 +HX0 3 =Hg 2 (N0 3 ) 2 + NO + H 2 0. 

(dilute) 

(4) Pb(N0 3 ) 2 + HC1 = PbCL 2 + HN0 3 . 



240 MSHOUBT. 

(5) AgN0 3 +HCl = AgCl + HN0 3 . 

(6) HgN() 3 + HC1 = HgCl + HN0 3 . 

(7) PbCl 2 + H 2 = Sol. of PbCl 2 . 

(8) PbCl 2 + K 2 Cr0 4 = PbCr0 4 + KC1. 

(9) AgCl + NH 3 =(NH 3 ) 3 (AgCl) 2 . 

(10) (NH 3 ) 3 (AgCl) 2 + HN0 3 = AgCl + NH 4 N0 3 . 

(11) Hg CI + NH 3 = NH 9 Hg,Cl + NH 4 CL 

(12) NH 2 Hg 2 Cl + NOCl 2 + CI + H 2 = HgCl 2 + N0 2 . 

(13) HgCl 2 + SnCl 2 = Hg + SnCl 4 . 

Sug. The precipitates are underscored. Let the student determine 
which of the substances on the right of the sign = are gases. 

Model Recitation. Equations 1, 4, 7, and 8 illustrate the reactions 
previously described in lead. No. 1 shows how lead is dissolved; Pb(N0 3 ) 2 
is the substance in solution; NO is a gas. No. 4 shows the precipitation 
of lead with HC1. PbCl 2 is the precipitate. No. 8 shows the distinctive 
test for lead (PbCr0 4 being yellow) which was separated from silver and 
mercury by No. 7. Give the name and the formula of each compound. 

EXERCISES. 

1. Observe that different products are obtained when some substances 
react, depending upon which substance is in excess. Thus, if Hg be in 
excess, silver amalgam is obtained in Exp. 134, while an excess of AgN0 3 
gives pure silver. What other instances have been given ? 

2. Read R, and S., Vol. II., Pt. I., pp. 388 to 392, for different processes 
of preparing mercury. 

3. Expose some freshly prepared AgCl to the action of sunlight. What 
changes in color occur? 

4. Compute the atomic heats and atomic volumes of lead, silver, and 
mercury. 

Note. The expression "group precipitate," as used in the text in connec- 
tion with a single metallic salt, signifies the precipitate of that metal 
obtained by the group reagent. 



CHAPTER XVI. 

THE SECOND GROUP METALS. 

250. The second group metals are those the sulphides 
of which are insoluble in dilute acids. These metals are 
separated from all others by removing the first group 
metals with hydrochloric acid, after which hydrogen sul- 
phide, H 2 S, is passed through the acidulated solution. 

Note. Tellurium and Selenium, which are precipitated with these 
metals, have already been described. Lead which has not been fully 
removed from the first group also appears in this group. 

The metals of this group exhibit many kindred proper- 
ties. Their oxides, excepting those of arsenic, are nearly 
insoluble in water ; they do not decompose water except 
at high temperatures, and then but four, viz., bismuth, 
antimony, tin, and molybdenum, give this reaction to any 
considerable extent ; all the commonly occurring metals 
form soluble nitrates (excepting antimony and tin, which 
form oxides) when treated with nitric acid ; all are 
readily reduced to the metallic state when heated on 
charcoal in the reducing-flame. 

In deference to some requirements in analysis, we may 
divide the common metals of this group into two divisions. 
The metals of the first division yield sulphides which are 
soluble in yelloio ammonium sulphide, (NH 4 ) 2 S 2 , while the 
sulphides of the second division are insoluble in that 
reagent. Let us distinguish these divisions by the letters 
A and B ; then eacli division is as follows : — 



242 AUSENIC. 



Mercury (in mercuric salts). 
Lead. 



f Arsenic. 
Division A-j Antimony. Division B^j Bismuth. 

[ Tin. | Copper. 

[ Cadmium. 
Note. The yellow ammonium sulphide for the purposes mentioned in 
this chapter may be prepared by gently warming in a test-tube a little 
reagent ammonium sulphide, (NHJ 2 S, with a small quantity of flowers of 
sulphur. The reagent sulphide, upon standing, also changes to the yellow 
variety. 

Division A. 

ARSENIC. 

Symbol, As iii,v . — Atomic Weight, 75. — Specific Heat, 
0.0822. — Melting-Point, 356°. 

251. Occurrence. — In nature arsenic occurs free in 
kidney-shaped masses, which usually may be split up into 
thin laminae or leaves ; but commercial arsenic is obtained 
chiefly from some of the following ores : Iron Arsenide, 
FeAs 2 ; Nickel Arsenide, Ni As; Mispickel, (FeS) 2 As; Re- 
algar, As 2 S 2 ; Orpiment, As 2 S 3 ; and from Arsenic Trioxide, 
As 2 3 , combined with lead, calcium, and cobalt as arsenites. 

252, Preparation. — Exp. 152 p. Make a pellet of arsenic 
trioxide, As 2 3 (commonly known as "arsenic"), with pow- 
dered charcoal and a drop or two of water. Place the pellet in 
the bottom of a hard glass test-tube, and heat gently to expel 
the water. Now insert a loosely-fitting stopper (made of chalk) 

i early down to the pellet, which is then to be heated to redness. 
Arsenic is freed and vaporized ; the vapors condense, above 
the chalk, on the sides of the test-tube, farming a metallic 
mirror. 

Exp. 15b p. Heat any arsenic compound, as As 2 3 , on 
charcoal before the reducing-flame. Arsenic is freed in form 
of a vapor which has an odor somewhat resembling garlic. 



ARSENIC. 243 

Similarly treat a bit of metallic arsenic. Do you obtain the 
same odor? How do 3011 now know that arsenic was freed by 
heating As 2 3 ? 

Commercial arsenic is prepared by heating its ores, 
especially mispickel and orpiment, in earthen vessels or 
tubes. The arsenic is driven off in vapors, which are 
condensed in sheet iron tubes or condensers. 

To purify the arsenic thus obtained it is sublimed with 
charcoal, when it condenses in rhombohedral crystals pos- 
sessing a bright metallic lustre. 

253. Properties, Uses, and Compounds of Arsenic. — 

Arsenic is a solid substance possessing a steel-gray color 
and a metallic lustre. When heated under ordinary 
pressure, it seems to vaporize without melting, at 356°; 
under greater pressure,' however, it may be obtained in a 
liquid state. 

As previously noted, arsenic stands midway between 
the metals and non-metals; in its chemical compounds 
and chemical deportment it is closely allied to phosphorus 
on the one hand, while, on the other hand, the physical 
properties of arsenic and its compounds bear a close re- 
semblance to those of antimony. 

Arsenic oxidizes quite readily in warm, moist air, form- 
ing a dark substance (probably a low oxide) known as 
j\y poivder. When strongly heated in oxygen, arsenic 
burns with a white light, forming arsenic trioxide, As 2 Q 3 . 
With oxygen and hydrogen, arsenic forms the acids 
ursenious acid, H 3 As0 3 (?), and arsenic acid, H 3 As0 4 , which 
closely resemble the corresponding acids of phosphorus. 

The vapors of arsenic possess a strong odor resembling- 
garlic. Both arsenic and its soluble salts act as deadly 
poisons when taken into the system, and even arsenical 



244 ARSENIC. 

vapors produce the symptoms of arsenic poisoning when 
inhaled or absorbed through the pores of the skin. 

The best antidote for arsenic is freshly prepared ferric 
hydroxide, Fe 2 (OH) 6 , made by adding ammonia to a solu- 
tion of ferric chloride, Fe 2 Cl 6 . The ferric hydroxide is 
filtered out and washed, when it is ready for use. Mag- 
nesia, MgO, is also an antidote ; both these substances 
form insoluble compounds with the arsenic, thus prevent- 
ing its absorption by the system. An emetic, such as a 
teaspoonful of mustard in a cup of warm water, should 
soon follow the antidote, and that in turn should be fol- 
lowed by castor oil. 

Arsenic is dissolved by nitro-hydro chloric acid or by chlorine 

water : — 

2 As + 5C1 2 + 8H 2 = 2H 3 As0 4 + 10HCL 

A good working solution of an arsenite can be made 
thus : — 
As 2 3 + 6 NaOH =-2 Na 3 As0 3 + 3 H 2 ( + an excess of NaOH) . 

THE PRINCIPAL COMPOUNDS OF ARSENIC ARE: — 

(a) Arsenic Trioxide, As 2 3 . This oxide is sometimes called 
arsenious anhydride, and is usually sold in drug stores as 
" arsenic." This a white crystalline powder, used for destroy- 
ing vermin, as a medicine, and in taxidermy as a dryer and 
antiseptic. Arsenious Acid, H 3 As0 3 , has not been isolated ; 
from it are derived the arsenites. All the soluble arsenites 
are poisonous. 

(b) Arseniuretted Hydrogen or Hydrogen Arsenide, AsII 3 , 
which is an exceedingly poisonous, inflammable gas evolved by 
treating any compound of arsenic with nascent hydrogen. The 
same apparatus used for hydrogen sulphide may be employed 
for this purpose. This gas is to be had by placing in the test- 
tube any arsenic salt together with metallic zinc and dilute 



AKSENIO. 245 

sulphuric acid. This gas is generated in making the " spot 
test " (Art. 254) for arsenic, and great care must be used not 
to inhale any of it. Allow the acid and zinc to work until the 
apparatus is free from air before adding the arsenic compound ; 
the gas escaping from the jet should be immediately ignited. 

(c) Scheele's Green or Copper Arsenite, CuHAs0 3 . This com- 
pound is to be had by adding an aqueous solution of arsenic 
trioxide to an ammonia-copper sulphate solution ; this latter 
solution is prepared by adding ammonia to a solution of copper 
sulphate until the precipitate, which is at first formed, dis- 
solves. 

Schweinfurth's Green is a copper aceto-arsenite, (CuOAs 2 3 ) 3 - 
Cu(C 2 H 3 2 ) 2 . Both of these compounds are used as pigments, 
and are sold under the name of Paris Green. Gardeners use 
them as anti-insect powders. Wall paper frequently owes its 
green tints to the presence of one of these compounds ; such 
paper is dangerous, sometimes giving rise to aggravated cases 
of arsenic poisoning. It seems that such papers give off 
arsenical vapors or dust, which are disseminated through the 
air and absorbed by the pores of the skin and by the lungs. 

(d) Arsenic Pentoxide, As 2 5 , and Arsenic Acid, H 3 As0 4 . 
The first is prepared by dissolving arsenic in strong hot nitric 
acid, after which the solution is first evaporated and then fused 
at a dark -red heat. Arsenic acid is obtained by treating arsenic 
with chlorine as previously explained. From this acid we 
obtain the arsenates. 

(e) Arsenious Sulphide, As 2 S 3 , is the group-reagent precipi- 
tate, and may be had by treating any soluble arsenic salt with 
hydrogen sulphide. This is a yellow powder soluble in yelloio 
ammonium sidplude, (NH 4 ) 2 S 2 = 

(/) Sodium Arsenate is used to remove the mordant in 
calico printing. The impure form thus employed is made by 
dissolving arsenic trioxide in sodium hydroxide, after which 
sodium nitrate is added ; the solution is then evaporated to 
dryness. (Read R. and S., Vol. II., Pt. I., p. 125.) 



246 ARSENIC. 

254. Tests for Arsenic and its Compounds. — 1. Metal- 
lic arsenic is to be distinguished bj^ its physical properties 
and by its giving a garlic odor when heated in the reduc- 
ing-flame on charcoal. 

2. Solutions or solids are best tested by the "spot or 
mirror test." The solid or solution is first treated with 
a crystal of potassium chlorate and hydrochloric acid to 
oxidize the arsenic (if any be present) to arsenic acid. 
The excess of chlorine is expelled, and the prepared solu- 
tion is now treated with arsenic-free zinc and dilute 
sulphuric acid. Hydrogen arsenide is thus evolved. The 
escaping gas is delivered through a jet and is ignited. 
Now hold a piece of cold porcelain in the flame. Arsenic 
if present is deposited on the porcelain as a bright steel- 
gray spot or mirror. 

Make several spots, and make sure that they are arsenic, 
thus : — 

Qa) Try one spot with a drop of yellow ammonium 
sulphide ; it turns yellow. 

(5) Try another with a drop of hydrochloric acid ; it 
does not dissolve, 

(Y) Add to another a drop of a solution of bromine or 
chlorine in potassium hydroxide ; it dissolves. 

(cT) Try another with hot nitric acid ; it dissolves clear. 
Then to this clear solution add a drop of silver nitrate ; 
no change in color occurs. Now treat the solution with 
ammonia vapor, which may be forced against the solution 
by blowing through a blow-pipe across the mouth of an 
uncorked ammonia bottle ; the solution turns brick-red or 
yellow. You may now be assured that arsenic in some 
form is present. 

3. To distinguish an arsenate from an arsenite. Make a 



ANTIMONY. 247 

clear solution of magnesium sulphate, MgS0 4 , ammonia, 
and ammonium chloride, NH 4 C1. To this clear solution 
add the unknown solution, a portion of which has been 
found to contain arsenic by 2. A white precipitate (in 
the absence of phosphates) indicates an arsenate. An 
arsenite gives a white precipitate with MgS0 4 which is 
soluble in ammonia and NH 4 C1. A solution of arsenic 
trioxide in an excess of sodium hydroxide, when treated 
with copper sulphate, gives a blue solution from which a 
red precipitate of Cu 2 is thrown down on boiling. 

Note. Any arsenic compound in solution gives a yellow precipitate, 
As 2 S 3 , with H 2 S. 

ANTIMONY. 

Symbol, Sb" ,,v . — Atomic Weight, 120. — Specific Heat, 
0.0523. — Melting-Point, 425°. 

255. Occurrence. — Native antimony occurs in small 
quantities as scaly masses which are contaminated with 
iron, silver, etc.; but its chief source is Stibnite, Sb 2 S 3 . 
Other ores of less importance also occur. 

256. Preparation. — Exp. 154 p. Make a pellet of a 
thoroughly pulverized antimony compound, as stibnite, Sb 2 S 3 , 
with potassium cyanide or with sodium carbonate and a drop of 
water. Heat on charcoal in the reducing-flame ; a bright 
metallic bead of antimony is obtained. Try the malleability, 
etc., of this bead as you did of the lead or silver bead. In com- 
parison, how does it behave? 

Exp. loop. Pulverulent antimony, or antimony black, may 
be prepared by placing a zinc strip in a solution of antimony 
chloride, SbCl 3 (see Art. 257, (c)). How does ths precipitate 
compare with those thus obtained in the first group metals? 
Preserve this powder for future use. 



248 ANTIMONY. 

Commercial antimony is prepared from stibnite. The 
crude ore is first melted in vessels the bottoms of which 
are perforated by small openings. The sulphide is melted 
and runs through these openings nearly pure. The sul- 
phide is next melted with metallic iron, which combines 
with the sulphur, leaving the antimony free and ready to 
be drawn off in a molten condition. 

By another process the sulphide is converted into an 
oxide in a reverberatory furnace. The oxide is then re- 
duced by heating it with charcoal or some other reducing 
agent. 

The antimony of commerce often exhibits a stellated 
surface, which is obtained by allowing the purified molten 
metal to cool slowly. 

257. Properties, Uses, and Compounds of Antimony. 

— Antimony is a bluish-white metal, so brittle that it may 
be finely pulverized. It tarnishes slowly in warm, moist 
air and burns with a white light when heated to redness 
in the air, forming the trioxide, Sb 2 3 . It vaporizes at a 
white heat in the absence of oxygen. 

Metallic antimony is used principally in making alloys, 
to which it imparts the property of hardness and that of 
expansion when cooling from a molten state. Hence it is 
extensively employed in manufacturing type-metal. 

Antimony is also used in many pharmaceutical prepara- 
tions. That form of antimony which is obtained in Exp. 
155, and which is an article of commerce, is employed to 
impart a metallic surface to plaster casts. It is also used 
as a medicine for horses. 

Exp. 156 p. Coat a small plaster of paris image with anti- 
mony black, and polish until the surface assumes a metallic 
lustre. 



ANTIMONY. 249 

With hydrogen and oxygen, antimony forms both acids 
and bases. With acids it forms salts, in which it plays 
the part of a trivalent metal, as in antimony sulphate, 
Sb 2 (S0 4 ) 3 . It also forms basic salts, in which the group 
SbO, which is univalent, takes the place of one atom of 
hydrogen. These are called antimonyl salts. Antimonyl 
sulphate, (SbO) 2 S0 4 , may serve as an example. The prin- 
cipal acid of antimony is antimonic acid, H 3 Sb0 4 , which 
closely resembles phosphoric and arsenic acids. 

The best solvent for antimony is hot nit ro-hydro chloric 
acid, and the salt thus obtained (SbCl 3 ) is a good solution 
for working purposes. 

THE PRINCIPAL COMPOUNDS OF ANTIMONY AEE : — 

(a) The oxides, Sb 2 3 , Sb 2 4 , and Sb 2 5 , which give rise to 
a series of acids similar to those of phosphorus. (Art. 220.) 

Antimonic Acid, H 3 Sb0 4 , is obtained by oxidizing antimony 
in nitric acid. None of these acids are employed for industrial 
purposes, although antimonic acid was formerly used as a 
medicine. 

(b) Tartar Emetic, C 4 H 4 KSb0 7 , which is used in medicine. 
It is prepared by dissolving antimony trioxide, Sb 2 3 , in cream 
of tartar or potassium tartrate, KHC 4 H 4 6 . 

(c) Butter of Antimony. Antimony Trichloride, SbCl 3 . This 
is prepared by dissolving antimony trisulphide, Sb 2 S 3 , in hydro- 
chloric acid. It is used in staining iron or steel utensils, such 
as gun -barrels. 

(ft) Stibnite, Antimony Trisnlplude, Sb 2 S 3 , which is one of 
the antimony ores and is of a dark-gray color. That which is 
obtained by precipitating an antimony salt with hydrogen 
sulphide is an orange-colored powder. It is a group-reagent pre- 
cipitate insoluble in dilute acids, soluble in ammonium sulphide* 
The pentasulphide, Sb 2 S 5 , resembles the trisulphide. 



250 ANTIMONY. 

(e) Hydrogen Stibide, SbH 3 . This is an inflammable gas 
used in the " spot test" for antimony. This is obtained from 
an antimony salt by treating it with zinc and sulphuric acid, as 
in preparing AsH 3 , Art. 254, 2. 

General Note. Antimony and its salts are poisonous when taken 
internally, but they are neither so dangerous nor so active as arsenic and 
its compounds. 

258. Tests for Antimony. — 1. Solids containing anti- 
mony may be tested in the reducing-flame with sodium 
carbonate on charcoal. A silver-white, brittle bead is 
obtained. 

2. A very delicate test for antimony, free or combined, 
is the "spot test." Make several spots by directly treat- 
ing the substance with zinc and dilute sulphuric acid. 
These spots are distinguished from arsenic spots by the 
color. Those of antimony are black or velvety-brown. 
More certain distinctions are as follows: — 

(a) The antimony spot with yellow ammonium sul- 
phide turns orange, 

(S) With hot nitric acid turns white. 

(V) In a solution of bromine or chlorine in potassium 
hydroxide it is insoluble. 

(d) The white spot, formed in (b), treated with silver 
nitrate and ammonia fumes gives no color; but when a drop 
of ammonia solution is added, the spot turns black. 

3. Upon addition of water to the solution of an anti- 
mony salt acidulated with hydrochloric acid, a portion of 
the antimony is precipitated as a basic salt soluble in 
tartaric acid. (See Art. 267, 2.) 

Note. H 2 S forms an orarz^e-colored precipitate, Sb 2 S 3 or Sb 2 S 5 , with 
any antimony compound in solution. 

Sug. See Chemical News, June 5, 1885, p. 267, and June 19, 1885, p. 
292, for some delicate tests for antimony. 



TIN. 251 



TIN. 



Symbol, SN iiiv . — Atomic Weight, 119. — Specific Heat, 
0.0548. — Melting-Point, 230°. 

259. Occurrence. — Small quantities of tin occur native. 
Its chief ore is Tin Stone, Cassiterite or stannic oxide, Sn0 2 . 
This ore occurs in veins in the older schistose and crystal- 
line rocks, and also as nodules or "stream tin " in the beds 
of rivers traversing the above-mentioned rocks. 

The principal tin mines of the world are in Cornwall 
(England), Australia, Bolivia, and Peru. The mines of 
Cornwall are the oldest tin-mines known ; they were 
probably worked as far back as during the Bronze Age. 

260. Preparation. — Exp. 157 p. Into a solution of a tin 
salt place a strip of zinc. What results? 

Exp. 158 p. Make a paste of a tin salt with solid potassium 
cyanide, KCy, and a drop of water. Heat this paste on char- 
coal before the reducing-flame. Small beads of tin are thus 
obtained with great difficulty. (See Art. 262, 2, for test for tin.) 

The first step in its preparation for commerce is to crush 
the ore and to remove as many impurities as possible by 
washing. The ore is then roasted in revolving, inclined 
cylinders through which a continuous blast of air and 
flame are passing. In this way volatile substances, such 
as arsenic and sulphur, are driven off, while other impuri 
ties are oxidized. The roasted ore is now washed again, 
and is thus obtained quite pure. It is now reduced to 
metallic tin by mixing it with anthracite and heating it in 
a blast-furnace. 

The metal is next drawn off and further purified by 
liquation, i.e., it is gradually melted in a reverberatory 



252 tin. 

furnace ; the pure tin is more fusible than its alloys, 
which are present, and melts first. It is then drawn off 
and stirred with poles of green wood ; a dross separates 
out and is removed. In this way the tin is brought to a 
state of great purity. 

Properties, Uses, and Compounds of Tin. 

261. Tin is a white, lustrous metal which is quite per 
manent in the air at ordinary temperatures and which, in 
the absence of oxygen, can be vaporized at a white heat. 
It is very malleable, and is extensively used in the form of 
thin sheets as tinfoil. When bent or bitten, bar-tin emits 
a crackling sound, supposed to be due to the motion of its 
particles over one another ; this goes to show that solid 
masses of tin probably assume a granular structure. 

Tin can be obtained in a crystalline form in different 
ways : (1) Melt it, and allow the molten mass partially to 
cool; pour off the liquid portion, when prismatic crystals 
of tin remain. (2) Decompose a chloride of tin, as SnC] 2 
or SnCl 4 , by means of a weak galvanic current. (3) Make 
a solution of a chloride of tin alkaline, and insert a bright 
strip of zinc. 

Since tin is quite readily reduced from its ores, it has 
been known from an early time. Its uses are many and 
its alloys are important. 

. Queries. What is "Block Tin"? What is tin plate, and how is it 
made ? What are the uses of metallic tin ? 

Tin as a base yields two series of salts, — the stannous 
and the stannic salts. These are well typified by the 
chlorides SnGl 2 and SnCl 4 . 

The tin acids yield two series of salts of small importance, 
— the stannates and the metastannates. 



tin. 253 

The lest solvent for tin is hydro chloric acid, stannous 
chloride, SnCL, being the salt produced. Nitro-hydro chloric 
acid (with excess of HC1) dissolves tin, forming stannic 
chloride, SnCl 4 . These are good ivorking solutions. 

THE PRINCIPAL TIN COMPOUNDS ARE : — 

(a) Tin Stone, or Cassiterite, Sn0 2 ; this is the principal ore 
of tin. 

Stannic Acid., H 2 SnO , may be supposed to originate thus : — 

Sn0 2 + H 2 = H 2 Sn0 3 . 
In practice this acid is obtained when calcium carbonate is 
treated with an excess of stannic chloride. One of the salts of 
this acid, sodium stannate, Na 2 SnO , is largely used (as " pre- 
paring salts ") in calico printing. 

Metastannic Acid probably has the formula IT 10 Su 5 O ]5 . Both 
these acids form salts chiefly with the metals of the fifth group. 

(b) Stannous Chloride, SnCl 2 , and Stannic Chloride, SnCl 4 . 
These salts are used as reagents in the laboratory. How are 
they made? 

(c) Stannous Sulphide, SnS, which is a brown powder, while 
Stannic Sidphide, SnS 2 , is a yellow one. These are the group- 
reagent precipitates, thrown down by hydrogen sulphide in acid 
solutions ; they are soluble in yellow ammonium sulphide. 

Query. If the solution be a stannic salt, which sulphide is obtained % 
A stannous salt 1 

262. Tests for Tin. — 1. Metallic tin is recognized by 
its lustre and by the crackling sound when bent or bitten. 

2. An unknown solid is tested by the blow-pipe, Exp. 
158. If the oxidizing flame be used, a coating of stannic 
oxide, Sn0 2 , is formed upon the charcoal around the assay. 
This coating is pale yellow when hot, white when cold. 

3. A solid insoluble in water is dissolved in hydrochloric 
acid, and mercuric chloride, HgCl 2 , is added (see Art. 246). 



254 tin. 

Note. At first a white precipitate is obtained, if a stannous salt be 
present ; this soon turns gray and then (usually after some time) black, 
when metallic mercury is found to have been precipitated. The white 
precipitate is probably Hg 2 Cl 2 . Write the equation. This reaction is of 
importance, since by it we may identify both tin and mercury. 

4. Aii unknown solution is tested by adding: — 

(a) HgCl 2 (see 3). 

(ft) H 2 S (see Art. 261 (<?)). 

(el) Ammonia and a zinc strip (Art. 261). 

Query. How can you distinguish between a stannous and a stannic 
salt ? 

263. To separate and identify Arsenic, Antimony, 
and Tin. — There is no simple method which is at the 
same time very accurate. A fairly good one is the fol- 
lowing: Bring the precipitate which contains the sul- 
phides of arsenic, antimony, and tin into a small flask, and 
boil with concentrated hydrochloric acid as long as the 
odor of hydrogen sulphide can be detected. The sul- 
phides of antimony and tin are dissolved, while the 
sulphide of arsenic remains undissolved. Filter and wash, 
and then treat the undissolved substance with hydrochloric 
acid and potassium chlorate. It is thus converted into 
arsenic acid, which may be detected by means of the 
reactions given in Art. 254, 3. Test also for arsenic by 

(a) The spot test (Art. 254, 2), 

(6) Hydrogen sulphide (a yellow precipitate) . 

The solution containing antimony and tin is treated 
with zinc, which reduces the compounds to the metallic 
state. After a time pour off the solution, wash the 
residue with water, and treat with hydrochloric acid. 
Only the tin is dissolved. It may be detected by means 
of mercuric chloride (see Art. 262, 3). Examine the 
residue and convince yourself that it is antimony by 



BISMUTH. 255 

(a) The spot test, 

(b) Hydrogen sulphide (an orange-colored precipitate). 

Sug. Write the equations for the steps involved. 



Division B. 

The metals of this division of the second group are 
those whose sulphides are not soluble in yellow ammonium 
sulphide. 

BISMUTH. 

Symbol, Bi m . — Atomic Weight, 208. — Specific Heat, 
0.0305.— Melting-Point, 270°. 

264. Occurrence. — Bismuth is a comparatively rare 
metal. It usually occurs native, but it is always contami- 
nated with a small percentage of other metals, such as 
iron, copper, lead, silver, etc. 

Of its ores Bismuth Ochre, Bi 2 3 , is the principal one. 
Bismuthite, Bi 2 S 3 , ranks next in importance. Most of the 
bismuth of commerce comes from Saxony. 

265. Preparation. — Exp. 159 p. Make a pellet of any 
bismuth compound with sodium carbonate and a drop of water. 
Heat it in the reducing-flame on charcoal. Try the bead as you 
did those of lead, silver, etc. What difference do you find? 
Treat the bead with the oxidizing-flame. Note the coating on 
the charcoal. This coating, BiX) 3 , is characteristic. 

Exp. 160 p. Into a solution of bismuth chloride, BiCl 3 , place 
a zinc strip, and proceed as usual. Try the same salt with the 
galvanic current. 

Bismuth can be extracted incompletely from its ores by 
fusion ; the extraction can be made complete by roasting 



256 BISMUTH. 

them first and afterward fusing them with iron, slag, and 
charcoal. The crude bismuth thus obtained is purified by 
melting it at the lowest possible temperature on an inclined 
plane ; the molten metal runs slowly down the plane while 
the impurities remain behind. 

Commercial bismuth is also prepared as in Exp. 160. 

266 Properties, Uses, and Compounds of Bismuth. 

• — Metallic bismuth is not employed in a pure state in 
any of the arts. It is chiefly used in alloys and in making 
pharmaceutical preparations; nearly 25,000 kilograms are 
thus consumed annually. 

Bismuth is a hard, brittle metal of a grayish-white color 
with a distinct tinge of red. It oxidizes but slowly in 
the atmosphere, but the gases of the laboratory cause it 
quickly to tarnish. 

It expands during solidification, and it imparts this 
property to its alloys, which aie, on this account, used in 
making delicate castings. Many of the alloys of bismuth, 
especially those with tin, lead, and cadmium, melt at very 
low temperatures (see Art. 230). These " fusible metals" 
or alloys are used in stereotyping and electrotyping ; they 
are also used as solders and for making safety plugs for 
steam boilers. 

Sug. Explain the use of the safety plug. 

Bismuth, like antimony, forms two kinds of salts, those in 
which its atom takes the place of three atoms of hydrogen, 
as in bismuth nitrate, Bi(N0 3 ) 3 , and those in which the 
group BiO, called bismuthyl, takes the place of one atom 
of hydrogen, as in the salt (BiO)(N0 3 ). Salts of the 
former class are decomposed by water and transformed 
into salts of the latter class, which are known usually as 
basic salts. 



BISMUTH. 257 

An acid called bismuthic acid, and supposed to have the 
formula HBi0 3 , has been described ; but very little is 
known regarding it or its salts. 

The best solvent for bismuth is nitric acid. Hydrochloric 
acid also reacts feebly with this meted. The solutions thus 
obtained are good working solutions. 

THE PRINCIPAL BISMUTH COMPOUNDS ARE AS FOLLOWS : 

(a) Of the Bismuth Oxides, Bi 2 2 and Bi 2 3 are the principal 
ones. Of these two the trioxide Bi 2 3 is the more important. 
It is the chief ore of bismuth, and is used as a pigment. 

(b) Bismuth Nitrate, Bi(N0 3 ) 3 + 3H 2 0, is obtained by dis- 
solving the metal in nitric acid. 

The JSub-nitrate of Bismuth, BiO.N0 3 , H 2 (of the pharma- 
copoeia) , ' is prepared by precipitating bismuth nitrate by 
the addition of water to the solution. The sub-nitrate is used 
in medicine as a remedy for cholera and dysentery. It is also 
used as a cosmetic, under the names of Blanc d'Espange and 
Blanc de Fard. It is further used in glazing porcelain, to 
which it imparts an iridescent surface. This salt is a white 
powder, now known as Bismuth Basic Nitrate. 

(c) Bismuthite, Bi 2 S 3 , is an ore of bismuth and the group- 
reagent precipitate . It is obtained from an acid solution of a 
bismuth salt by passing through it hydrogen sulphide. It is 
soluble in hot nitric acid. 

267. Tests for Bismuth. — 1. Unknown solids are tested 
for bismuth by the blow-pipe. When the bead is treated 
with the oxidizing-flame, Bi 2 3 is formed, and the charcoal 
is coated orange-yellow while hot, lemon-yellow when 
cold. The edges of the coat are bluish-white when cold. 

2. A solution is tested by adding : — 

(a) Water, which yields a basic salt, as a white pre- 
cipitate insoluble in tartaric acid. (See Art. 258, 3.) 



258 copper. 

(b) H 2 S, a black precipitate, Bi 2 S 3 , soluble in HN0 3 . 

(c) Ammonia, a white precipitate, Bi(OH) 3 . 

(d) K 2 Cr 2 7 , a yellow precipitate (BiO) 2 Cr 2 7 , which is 
insoluble in KOH, a distinction from lead. 

■(e) KI in acid solution gives Bil 3 , a brown, unstable 
precipitate soluble in an excess of HC1. 



COPPER. 

Symbol, Cu f » ". — Atomic Weight, 63.6. — Specific Heat^ 
0.0952. — Melting-Point, 1090°. 

268. Occurrence. — - Copper occurs native in large 
quantities, and the commercial metal is obtained princi- 
pally from this source. The most plentiful deposits are 
found in upper Michigan, where masses of the pure metal 
weighing many tons have been found. It occurs in sheets 
or veins, intersecting red sandstone and trap rocks, but 
the largest deposits are found as granular masses mixed 
through a rocky matrix. Native copper also occurs in 
many other localities, and nearly every deposit is silver 
bearing. 

The ores of copper occur plentifully and are widely dis- 
tributed. The principal ores are : Cuprite, Cu 2 ; Copper 
Glance, Cu 2 S ; Malachite, CuC0 3 + Cu(OH) 2 ; Azurite, 
2CuC0 3 + Cu(OH) 2 ; and Copper Pyrites, CuFeS 2 . 

The argentiferous copper ores of the Rocky Moun- 
tains, especially those of Montana, have of late years 
furnished a large amount of the copper in the market, at 
times so reducing the price of the metal as to necessitate a 
temporary suspension of the mines till a higher price 
would render the mining and smelting of the ores more 
profitable. 



copper. 259 

269. Preparation. — Native copper usually requires 
little treatment except smelting; but the reduction of its 
ores to obtain commercial copper is a somewhat complicated 
process of minor interest, at present, to the American 
student. From its soluble salts copper maybe obtained 
by precipitation and by electrolysis. * 

Exp. 161 p. Place a bright strip of iron in a solution of 
copper sulphate, CuS0 4 . It is soon coated with a film of metallic 
copper. Thus try a strip of zinc. What result? Try two 
strips at once, one of zinc and one of iron. What result? 
Does the iron increase in weight owing to the deposit of cop- 
per? In what ratio? 

We have many familiar examples of the reduction of 
copper from the solution of its salts. In gravity batteries 
the copper plates are soon covered with a deposit of 
copper ; in electrotyping, a metallic film is deposited upon 
a wax mould of the type, and this film is afterward strength- 
ened by a fusible metal (it is thus that the plates were 
prepared from which these pages were printed) ; the hypo- 
phosphites, when heated with the solution of a copper salt, 
reduce metallic copper ; and the following metals will give 
metallic copper with a solution of a copper salt : iron, 
zinc, cobalt, nickel, lead, cadmium, bismuth, and tin. 

270. Properties, Uses, and Compounds of Copper. - 

Owing to its abundance in the native state, copper was 
probably the first metal used by man. The prehistoric 
copper miners of Lake Superior employed the rudest 
methods imaginable for mining and working copper. 
They confined their operations chiefly to the sheet-like 
veins which were visible at the surface. Owing to the 
dip of the rocks only the edge of the sheet was within their 
reach. They built wood fires upon the rocks until the 



260 COPPER. 

stone would crumble and leave a narrow ribbon of copper 
exposed ; then, by means of a stone from the lake shore, 
which served as a hammer, the ribbon was hammered off 
into strips, which were afterward rudely fashioned, by 
means of two stones — one a hammer, the other an anvil — 
into knives, spearheads, arrow-points, fish-hooks, needles, 
and other utensils. The relics of the ancient copper miners 
are found in all parts of America, and some of the richest 
mines in the world are located upon the sites of prehistoric 
mines. 

Copper is a tough, malleable metal of a reddish color 
which tarnishes quickly in air containing moisture and 
carbon dioxide. In the native state it sometimes occurs 
in regular octahedral crystals, which are also obtainable 
by the electric current. Copper forms two series of salts 
and no acids. 

Sug. Examine the copper plates of a gravity battery which has been 
in operation several weeks. 

Exercise. Write an essay, giving the uses of copper and describing 
the process of electrotyping. 

The best solvent for copper is nitric acid, and a solution of 
the salt thus obtained is a good one for practice. Copper 
sulphate solution ansivers the same purpose. 

THE PRINCIPAL COMPOUNDS OF COPPER ARE: — ■ 

(a) Copper Sulphate, or Blue Vitriol, CuS0 4 + 5 H 2 ; this 
salt is used in electrotyping, in calico printing, in the prepara- 
tion of Paris green, and for galvanic batteries. How is it 
prepared ? 

(b) Copper Nitrate, Cu(N0 3 ) 2 , which is used in calico print- 
ing. How is it prepared? 

(c) Cupric Suljjhide, CuS, and Ciqrrous Sulphide, Cu 2 S, 
which are the group-reagent precipitates. These are ohtained 



COPPER. 261 

by passing hydrogen sulphide through the solutions of the cor- 
responding copper salts. 

(d) The principal Oxides of copper, Cuprous Oxide, Cu 2 0, 
and Cupric Oxide, CuO. The former is used to impart a red 
color to glass ; it occurs native. Cupric oxide is used in color- 
ing glass green in imitation of the emerald. This oxide also 
occurs native as Melaconite. Both oxides may be prepared 
artificially. (See R. and S., Vol. II., Pt. L, pp. 329 and 330.) 

General Note. The copper salts act as poisons when taken internally. 

271. Tests for Copper. — 1. Any compound of copper 
may be reduced on charcoal, by the usual method, to 
minute red metallic beads. 

2. Solutions are tested thus: (a) Make a borax bead 
upon a platinum wire ; moisten with the solution and heat 
in the oxidizing-flame. If copper be present, the bead will 
be green while hot, blue when cold. (6) To the solution 
add : — 

(1) An excess of ammonia, a blue solution ; 

(2) H 2 S, a black precipitate. 

3. Potassium ferrocyanicle, K 4 FeCy 6 , in dilute solutions 
gives a reddish-brown solution; in concentrated solutions, 
a precipitate, Cu 2 FeCy 6 , of the same color. 

4. Copper chloride colors the Bunsen flame blue. 

Note. The tests by the blow-pipe for copper are as unsatisfactory as 
those for tin; the reduction occurs, "but the beads are of microscopical 
dimensions. If the fused mass be rubbed in a mortar spots of copper 
become visible when the flux and charcoal are removed by washing. 

272. To separate and identify Bismuth and Copper. 

— If the substance is a solid, dissolve it in nitric acid; 
then add an excess of ammonia. Bismuth hydroxide, 
Bi(OH) 3 , is obtained as a white, flocculent precipitate 
powder, while the copper remains in the blue solution as a 
cupro-ammonium salt. Filter out the precipitate, dissolve 



262 CADMIUM. 

it in hydrochloric acid and expel the excess of acid ; again 
add water, when bismuthyl chloride, BiOCl, is precipitated 
as a white powder. This identifies the bismuth; the blue 
solution identifies the copper. 

CADMIUM. 

Symbol, Cd". — Atomic Weight, 112. — Specific Heat, 
0.0567. —Melting-Point, 315°. 

273. Occurrence. — Cadmium is a somewhat rare metal, 
which is found in nature associated with zinc. Its sul- 
phide, CdS, or Greenockite, also occurs in small quantities. 

274. Preparation. — In smelting zinc, the cadmium is 
oxidized to form the compound CdO, which readily passes 
off in dark-yellow vapors. These vapors are condensed in 
suitable chambers, and afterward reduced to a metallic con- 
dition by heating in closed tubes with charcoal. The impure 
metal thus obtained is purified in the wet way, as in : — 

Exp. 162 p. Dissolve a bit of cadmium in hydrochloric acid. 
AJter expelling any excess of acid, suspend a strip of zinc in 
the solution. The cadmium is precipitated as a spongy, gray 
precipitate. Collect, fuse to a bead, then oxidize strongly. 
What occurs ? 

275. Properties, Uses, and Compounds of Cadmium. 

— Cadmium was discovered in 1817 by Stromeyer in zinc 
carbonate from Salzgitter. It is a tin-white metal, which 
vaporizes at 860°. It oxidizes slowly in the air, and the 
surface of the metal is apt to present a yellowish tint, 
owing to the formation of the oxide, CdO. It takes fire 
if vaporized in the air. 

Cadmium closely resembles tin in its physical properties ; 
but, unlike tin, it has but few uses in the arts. Cadmium 



CADMIUM. 263 

amalgam is used in filling teeth, since it is pasty at first, 
but afterwards hardens. 

The best solvent for Cadmium is nitric acid, In hydro- 
chloric acid and sulphuric acid it dissolves less readily. 
Employ the nitrate or the chloride as a ivorking solution. 

THE PRINCIPAL COMPOUNDS OF CADMIUM APE : — 

(a) Cadmium Oxide, CdO. How is this compound formed ? 

(b) Cadmium Iodide. Cdl 2 , which is used in photography ; 
it is prepared by boiling metallic cadmium and iodine in water. 

(c) Cadmium Sulphate, 3 CdS0 4 + 8 H 2 0, used in medicine 
in diseases of the eve. 

(d) Cadmium. Sulphide, CdS, used as a yellow pigment. It 
occurs native, as GreenocMte. and is the group-reagent precipi- 
tate thrown down by hydrogen sulphide in acid solutions. 

276. Tests for Cadmium. — 1. A solid heated on char- 
coal in the oxidizing-flame gives brownish-yellow fumes of 
CdO, also a coating of the same on the charcoal, if 
cadmium be present in sufficient quantity. 

2. An acidulated cadmium solution with hydrogen sul- 
phide gives a yelloio precipitate insoluble in yellow am- 
monium sulphide. 

3. A cadmium salt colors the borax bead yelloiv while 
hot, colorless when cold. 

277. To separate and identify Bismuth, Copper, and 

Cadmium. — 1. To the solution containing salts of these 
three metals add ammonia in excess. The bismuth is 
precipitated, and identified as in Art. 272. The copper 
and cadmium remain in solution. The copper is identified 
by the blue solution. 

2. Separate the copper and cadmium remaining in 



264 CADMIUM. 

solution thus: precipitate these two metals by hydrogen 
sulphide ; filter out and wash the precipitate, then add 
hot dilute sulphuric acid to the precipitate on the filter- 
paper; the copper sulphide is unaltered, while the cad- 
mium sulphide is dissolved and runs through, thus 
effecting the separation. Or, to the ammoniacal solution 
containing copper and cadmium add potassium cyanide 
until the blue color is destroyed ; then pass hydrogen 
sulphide into it, and the cadmium is precipitated as the 
yellow sulphide, CdS, to be further identified by Art. 276. 

Note. Copper sulphide is soluble in potassium cyanide, forming the 
double cyanide 6 KCy . Cu 2 Cy. Cadmium forms a similar cyanide, but it 
is decomposed by hydrogen sulphide. 

278. To separate and identify the Metals of the 
Second Group. — Acidulate the solution containing the 
salts of one or all of these metals with hydrochloric acid, 
and precipitate by hydrogen sulphide. The precipitate 
may be a sulphide of arsenic, antimony, tin, bismuth, cop- 
per, or cadmium ; or sulphides of them all. 1 

Wash the precipitate, and wash it through into an 
evaporating dish ; add yellow ammonium sulphide, and 
digest for some time, when the sulphides of division A 
dissolve, while the sulphides of division B remain un- 
altered. Filter and treat the filtrate as in 1, the remaining 
precipitate as in 2. 

1. Add hydrochloric acid to the filtrate. This decom- 
poses the compounds present, and precipitates the sulphides 
of tin, arsenic, and antimony. Filter out and wash the 
precipitate, and proceed according to Art. 263. 

2. Dissolve the precipitate while on the filter-paper in 
hot nitric acid, and expel the excess of acid by evaporat- 

1 Sulphides of lead and mercury may also be present. 



REACTIONS IN GROUP II. 265 

ing the solution to dryness. Dissolve in water, and pro- 
ceed by Art. 277, for bismuth, copper, and cadmium. (See 
Note 2.) 

Note 1. Should the precipitate fail to dissolve completely in HN0 3 , the 
residue is probably mercury, which was present in the original solution as 
mercuric salts. Therefore dissolve this residue in nitro-hydrochloric acid, 
and test by adding SnCl 2 . (See Art. 246.) 

Note 2. Before trying for bismuth, copper, and cadmium, be sure 
there is no lead salt in the solution. It is best to try a small portion of 
the solution with H 2 S0 4 for lead ; should a precipitate occur, add H 2 S0 4 
to the whole, which will remove the lead as a precipitate. Filter, and 
proceed with the solution by 277. 

279. Separation of the Metals of Groups I. and II. — 

To a cold solution containing one or more metals of both 
groups add hydrochloric acid ; the first group is precipi- 
tated, but not completely. (See Notes 1 and 2, Art. 278.) 

280. Reactions in Group II. — Balance the following 
equations, and ascertain what operations they indicate, 
and what principles they illustrate : — 

(1) As + Cl+H 2 0==H 3 As0 4 +HCL 

(2) As 2 3 + HC1 = AsCl 3 + H 2 0, 

and AsCl 3 + H 2 = H 3 As0 3 + HC1. 

(3) Sb+Cl=Sb€l 3 . 

(4) Sn + HC1 = SnCl 2 + H. 

(5) Bi+HN0 3 -Bi(N0 3 ) 3 + N0 2 +H 2 0. 

(6) Cu + HN0 3 = Cu(N0 3 ) 2 +NO + H 2 0. 

(7) Cd + HN0 3 = Cd(N0 3 ) 2 + NO + H 2 0. 

(8) H 3 AsO A + H 2 S = As 2 S 3 + H 2 + S 2 . 

(9) SbCl 3 + H 2 S = Sb,S 3 + HCL * 

(10) SnCl 2 + H 2 S = SnS + HCL 

(11) Bi(NQ 3 ) 3 + H 2 S = Bi 2 S 3 + HNQ 3 . 

(12) Cu(XQ 3 ) 2 + H 2 S = CuS + HNO s . 

(13) Cd(NO ai ) 2 + H 2 S = CdS + HNO,. 



266 



THE RARE METALS OF GROUP II. 



(14 
(15 

(16 

(1< 
(18 

(19 

(20 
(21 
(22 
(23 
(24 
(25 
(26 
(27 
(28 
(29 
(30 
(31 
(32 
(33 
(34 
(35 



As 2 S 5 + CI + H 2 = H 3 As0 4 + HC1 

Sb 2 S 5 + CI + H 2 = H 4 Sb 2 0- + HC1 

SnS + Cl = SnCl 4 + S. 

H 3 As0 4 + H = AsH 3 + H 2 0. 

AsH 3 + AgN0 3 + H 2 = H 3 As0 3 + Ag + HN0 3 . 

H 4 Sb 2 7 + H = SbH 3 + H 2 0. 

SbH 3 + AgMX = Ag 3 Sb + HN0 3 . 

SnCl 2 + Zn =_Sn + ZnCl 2 . 

PbS + HN0 3 = Pb(N0 3 ) 2 + S + NO + H 2 0. 

Pb(M) 3 ) 2 + H 2 S0 4 = PbSQ 4 + HN0 3 . 

Bi 2 S 3 + HX0 3 = Bi(N0 3 ) 3 + S + NO + H 2 0. 

Bi(N0 3 ) 3 + NH 4 HO = Bi(OH) 3 + NH 4 N0 3 . 

Bi(OH) 3 + HC1 = BiCl 3 + H 2 0. 

BiCl 3 + H 2 = BiOCl + HC1 

CuS + HNO a = Cu(NO.,) 2 + S + NO + H 2 0. 

Cu(N0 3 ) 2 + NH 4 HO = Cu(NH 3 ) 2 0, NH 4 NQ 3 + H 2 0. 

CdS + HN0 3 - Cd(N0 3 ) 2 + S + NO + H 2 0. 

Cd(N0 3 ) 2 + H,S = COS + HN0 3 . 

Sn + HM) 3 = SnQ 2 + H 2 + NO. 

Sn + HNO3 = Sn(N0 3 ), + H 2 -f NH 4 N0 3 . 

Sb + HNO. = Sb 2 Q 3 + H 2 + NO. 

Sb + HN0 3 = Sb0 2 + H 2 + NO. 



Queries. Which equations show the precipitation of Group II. 



Which show special reactions or tests 



THE RARE METALS OF GROUP II. 



GOLD. 

Symbol, Au m . — Atomic Weight, 197.2. 

281. Gold usually occurs native owing to its feeble chemical 
affinity ; it has been known since the earliest times, therefore, 
and ever highly prized. It occurs very widely distributed in 
the older sedimentary and igneous rocks, and rivers running 



GOLD. 267 

through these rocks wash down fine particles of gold and sand. 
From these sands the miner separates the precious metal by 
washing in a shallow pan or cradle. Nuggets of gold of great 
value have been found in the various gold-bearing districts, 
especially in Australia. The largest deposits of gold are in the 
western United States and Australia. 

Gold-mining by hydraulic power has been conducted on 
an enormous scale in the West. The auriferous deposits are 
loosened by powerful streams of water which are directed 
against them. Thus the detritus is loosened, and afterward 
carried down the mountain slopes in sluices in which are placed 
pockets containing mercury. The line particles of gold are 
caught in the pockets, as they readily form an amalgam with 
mercury. 

In quartz-mining, the coarse rocks are crushed by machinery, 
and the gold likewise extracted by amalgamation. 

Gold may be obtained in a pure state by first dissolving any 
of its alloys in nitro-hydrochloric acid, when its principal salt, 
AuCl 3 , is formed, and by then adding ferrous sulphate, FeS0 4 , 
thus : — 

2 AuCl 3 + 6 FeS0 4 = 2 Au + 2 Fe 2 (S0 4 ) 3 + Fe 2 Cl 6 . 

The finely divided gold thus obtained may be fused to a yellow 
bead on charcoal. 

The uses of gold are many, but in a pure state it is too soft 
to wear well, hence it is alloyed with silver and copper. Gold 
is very malleable and ductile, and does not tarnish in the air. 
Its salts are few and of little interest to the beginner. Name 
the uses of gold. 

The test for gold is the formation of the purple of Cassius, 
thus : — 

Dissolve the substance in aqua-regia, and expel the excess 
of acid. Fill a test-tube half full of water, then add one drop 
each of stannous chloride, SnCl 2 , and stannic chloride, SnCl 4 ; 
then add a few drops of the solution first made. If gold be 



. J8 fla: 

resent . a j ■ - - . - . ; _ ts be in 

Vr»Ti ... ----- . - - . 

i 

7LATLNUM. 

- v P: — At r . : "- :-: t . ] 

2S2 I-.::: .- > s:i "t: -~ intt . '.t.stttn- tt.etal :>f great value 
fa :he chen > without it, many \. „.. si pi esses wc dd 
: i"_i : ss: le. : ■_ ". : - kn ~ lr "_ : : tie rate eirntrnt- — : \ ". be 
'. - — e xt r a ~. e ;" 

D -yas probata 1 aboat three hundrt usage 

tttt its vn:; ::ics an:I nrer .a: at: tn n mr 

n:te ::.: :: :.: :t : ; . 

1 rs ""_". '_ ? y^rtir: ^"i:: sev 

metals itocc rs in many localities. but in small quanti: - 

I'. "v. ram is ~ained from its jres by first iissolvmg 
; t - : : -_z ' • ~ "".'.---"- ] i: tint: ilitttdr. PtCi__. is t: t:t:ei\ * " gethe: with 
the chic: ides of the accc mpanying me! Is tnmoniurn ehl 
±t': :":".-:'. — ..-::. : ;". it ;itio::tr :: t".atin".n: ana f.n::::";:; 
is pre ■:•:; - ita: ; ■ NHAPtCI This pn ipitate when heated 

yields - _ platinmL. is afterwards fused in lime 

... - : n :: - _ . - . 

El high melting-] I platinum and its power of i sast _ 
the action of solvents - . its malleability loe- 

r it most efnl in chemical labo es 

ised is _ ..--. foil --.-.. andbles. weights, : 
1 ainuni maj e wekk 1 life fa n It possesses a i emarka 

. . ";■ " : : nden sing: gases "nan its * — -: . : '.". — -hen 

in a spongy state is i thfbited when a bu ; _ gas 

is directed against i: : _ .. -thus gnif I. Platinum 

a :• ts s ina '. i at '. 7 ■:.."-:... - i ga: 15 ; 



PALLADIUM. 269 

when a heated spiral is held in the fumes of ammonia or ether : 
the wire continues to glow, so great is the action upon its sur- 
face. 

The salts of platinum are very numerous, but as they are used 
very little, they need not be considered here. 

Nitro-hydroehloric acid is the best solvent for this metal. 

The test for plat inum is made thus : — 

Dissolve the substance in aqua regia. expel any excess of 
acid, add NH 4 C1, when a yellow crystalline precipitate is thrown 
down, thus : — 

PtCl 4 + 2 XH 4 C1 = (NH 4 ) 2 PtCl 6 . 

Spongy platinum is to be had from this precipitate upon heating 
strongly. 

General Xote. Do not fuse any of the salts of the easily reducible 
metals on platinum, since they form fusible alloys with it, as will the 
silicon in charcoal, when platinum is heated in contact with the glowing 
coals. Do not heat a platinum crucible in a smoky flame, which will 
cause it to blister. 

Try the purity of platinum by boiling in HC1, then in pure 
HX0 3 . It should not dissolve. 

To clean a platinum crucible, fuse acid potassium sulphate, 
KHSO,, in it. 

PALLADIUM. 

Symbol, Pd". — Atomic Weight, 106.5. 

283. Palladium, a silver-white metal resembling platinum, 
occurs in connection with gold and platinum ores. It was first 
prepared by Wollaston, in 1804. Its uses in the arts are few, 
the chief ones being to make graduated scales for astronomical 
instruments, to plate silverware, and to take the place of gold 
in dentistry. Its best solvent is nitric acid, but spongy palladium 
is readily soluble in hydrochloric acid. The nitrate and chloride 



270 RUTHENIUM. — IRIDIUM. 

of palladium are used to separate chlorine, bromine, and iodine ; 
but these reagents are too expensive for general use. 

Palladium is detected by adding potassium cyanide to its 
solution in hydrochloric acid. A yellowish-white precipitate, 
soluble in hydrochloric acid and ammonia, is thrown down. It 
also gives a black precipitate with potassium iodide insoluble in 
hydrochloric acid. 

RUTHENIUM. 
Symbol, Ru". — Atomic Weight, 101.7. 

284. Ruthenium also resembles platinum. It was discovered, 
in 1845, by Claus, in the Ural platinum ores. It is very little 
used in the arts, nor are its salts particularly valuable. 

Ruthenium is detected by passing hydrogen sulphide through 
its solution : the solution turns blue, afterwards brown. Also, 
when water is added to its chlorides, an inky, soluble oxy- 
chloricle is formed. 

IRIDIUM. 

Symbol, Ir". — Atomic Weight, 193. 

285. Iridium occurs, as the preceding metals, in small grains, 
alloyed with platinum or osmium. It .forms a valuable alloy 
with platinum, consisting of 1 part iridium and 9 parts plati- 
num, which is very hard, elastic, insoluble, and unchanging in 
the air ; it also takes a splendid polish and has a small coeffi- 
cient of expansion, hence its use in making the standard measure 
of the metric system. Iridium alloys dissolve in aqua regia. 

Iridium is very refractory ; but it may be fused (as a phos- 
phide) at a high temperature by the addition of phosphorus. 
The phosphide is adapted to many purposes where hardness 
and the property of resisting chemical action are requisite. 
The phosphorus can be withdrawn, however, by repeatedly 
heating the phosphide in contact with lime. Iridium or the 
compounds mentioned are used for the tips of gold pens, for 



RHODIUM. — OSMIUM. — TUNGSTEN. 271 

"stylographic pens," and sometimes for the bearings of chem- 
ical balances. For valuable information concerning Iridium 
see The Chemical News for Jan. 1, 1885, p. 1, and Jan. 9, 
1885, p. 19. 

Iridium is detected by the dark-red crystalline precipitate 
formed by adding ammonium chloride to its concentrated solu 
tions. 

RHODIUM. 

Symbol, Rh". — Atomic Weight, 103. 

286. Rhodium also occurs with platinum, and was discovered 
in 1804 by Wollaston. It remains in solution after precipi- 
tating the platinum with ammonium chloride, and is to be 
obtained from this liquor. It is but slightly soluble in any 
solvent, but its alloys are soluble in aqua regia, when the pro- 
portion of rhodium is very small. 

Rhodium is reduced from acid solutions by metallic zinc. 

OSMIUM. 
Symbol, Os". — Atomic Weight, 190.8. 

287. Osmium likewise occurs with platinum, and is remark- 
able as forming a volatile oxide, Os0 4 . This metal is the 
heaviest substance known, its specific gravity being 22.477. 
It has never been fused. An alloy of osmium and iridium is 
used to tip gold pens ; also to make the bearings of mariner's 
Compasses. 

Osmium is detected by the odor of its volatile compound, 
Os0 4 , obtained by treating its soluble compounds with nitric 
acid. 

TUNGSTEN. 

Symbol, W iv . — Atomic Weight, 184. 

288. Tungsten occurs most plentifully in Wolfram , a tungstate 
of iron and manganese, and has not been prepared in a coherent 
state. Its proposed industrial use is to improve tool steel. 



272 MOLYBDENUM. 

Tungsten is detected by first fusing an}' of its compounds 
with potassium hydroxide, and afterwards dissolving the fused 
mass in hydrochloric acid ; into this solution a strip of zinc is 
immersed ; the solution turns blue if tungsten be present. 

MOLYBDENUM. 

Symbol, Mo". — Atomic Weight, 96. 

289. Molybdenum is a silver- white metal, occurring in Molyb- 
denite, MoS 2 ; this sulphide was mistaken, in ancient times, 
for plumbago, which substance it closely resembles. Ammo- 
nium molybclate is an important test for phosphoric acid (see 
App.) . Ammonium phospho-molybdate, 2 (NH 4 ) 3 P0 4 + 22 Mo0 3 
-f- 12 H 2 0, is used in chemistry as a reagent for detecting alka- 
loids. 

Molybdenum is detected in the same way as tungsten, the 
solution turning successively blue, green, and brown. 

EXERCISES. 

1. Dissolve in nitric acid a small silver coin, and see what metals you 
can detect in the solution. 

2. Allow a drop of molten bismuth to fall upon the floor, and note what 
occurs. 

3. What metals have atomic weights of about 104 1 About 195? Find 
their positions in the table on p. 221. By what similarity of properties are 
they marked 1 

4. How can you show by the same table that iron, cobalt, nickel, chro- 
mium, manganese, and copper are closely related 1 

5. What elements are closely related to phosphorus ? 

6. Dissolve a bit of worn-out "gold" jewelry in aqua regia and 
determine what metals are present. 

7. Compute the atomic heat and the atomic volume of the common 
metals of the second group. 

8. Analyze a sample of " antimony black " obtained from the drug 
store. 

"Pulverised Sb 2 S 3 is known as ' antimony black * although a mixture of 
anthracite and marble is sometimes sold under that name." — -Warder. 



CHAPTER XVII. 

THE THIKD GROUP METALS. 

290. The metallic hydroxides and sulphides of this 
group are soluble in dilute acids, but insoluble in alkaline 
solutions. There are different methods of separating this 
group from the other groups ; and, moreover, the individ- 
ual metals of the third group may be separated and 
identified by different processes. We shall here pursue 
that plan which is as simple as possible, and which is in 
most cases preferable. Just as in the preceding group, 
we may likewise divide the commonly occurring metals of 
this group into two classes. We may obtain the precipi- 
tates of this group as follows : Suppose the solution con- 
tains any or all the metallic salts of the five groups. The 
first and second group metals are removed by hydrochloric 
acid and hydrogen sulphide ; in any chromium compound 
that may be present chromium is now combined as a base 
through the agency of the reagents employed, while iron 
salts by the same means are reduced to the ferrous con- 
dition. In case no first and second group metals are 
present, it is still necessary to use hydrochloric acid and 
hydrogen sulphide to insure that chromium maybe present 
as a base (Art. 303, 4, Note). The solution is now boiled 
to expel any excess of hydrogen sulphide ; then nitric acid 
is added and the whole boiled a moment to oxidize iron 
salts to the ferric condition ; the solution is now ready for 
the application of the group reagents. 



274 THE THIRD GROUP METALS. 

Ammonia and ammonium chloride are immediately 
added ; thus the hydroxides Fe (OH) 3 , Cr (OH) 3 , and 
Al (OH) 3 are precipitated. This precipitate is now re- 
moved by filtering. To the filtrate ammonium sulphide, 
(NH 4 ) 2 S, is added; this gives the precipitates NiS, Co?, 
MnS, ZnS. Let us indicate these divisions as in the 
previous group : — 

r Nickel. 

f ^ ron - In h It 

Division Aj Chromium. Division B^ ° a " 

i Manganese. 
I Aluminum. [ 7 - 

Sug. Try to determine why it is necessary to oxidize ferrous to ferric 
salts, and why chromium, if present, must be a base. 

The most strongly marked characteristics of the metals 
of this group are as follows : — 

(<x) Their surfaces gradually oxidize in the air, forming 
oxides most of which are to be reduced to the metallic state 
only at a white heat in the presence of reducing agents. 

(J) On charcoal many of these metals cannot be readily 
reduced from their compounds by means of the blow-pipe. 

(e) Their oxides and lrydroxides are insoluble in water: 
in certain cases, however, the hydroxides are soluble in an 
excess of the alkali used as a precipitant. 

(<i) None of the common metals of this group give 
spectra or color the flame unless the temperature be 
higher than that of the Bunsen flame. 

(e) Most of these metals give a characteristic color to 
the borax or microcosmic bead, when heated on a platinum 
loop before the blow-pipe. 

General Note. Most of the common metals of the third group and 
those of the fourth and fifth cannot be reduced to the metallic state by 
any means likely to be at the command of workers in small laboratories. 
On this account, and by reason of the fact that the general principles un- 



iron. 276 

derlying the reduction of the metals have been illustrated previously, the 
attention of the student may now most profitably be given to the analyti- 
cal reactions of the various metallic salts. In case time permits, it would 
also be well to encourage the student to prepare such of the salts as the ap- 
paratus, chemicals, etc., at his command will permit. Owing to his previous 
training, the student will now be able, in his work, to devise methods and 
to keep his notes accurately and intelligently. In furtherance of this objecv 
many topics, by aid of the descriptions given, may be rewritten by him h* 
the form of experiments. Let him also make tables for each metal show- 
ing the effect of precipitants and solvents upon the salts of that metal. 



IRON. 

Symbol, Fe". — Atomic Weight, 56. — Specific Heat, 
0.1140. — Melting-Point, a white heat. 

291. Occurrence. — Natiye metallic iron occurs in in- 
significant quantities, and as meteoric iron ; it is also said 
to fall everywhere and constantly upon the earth as a fine 
dust. Meteorites frequently contain iron ; the largest 
mass on record weighs 32,000 pounds, while others of less 
weight are frequently found. 

The iron compounds are present in most rocks and soils, 
and play an important part in the animal and the vegetable 
economy ; the color of the blood and of all vegetation is 
due to the presence of iron. 

The ores of iron, from which the metal is reduced, 
usually occur in somewhat limited areas, but in many 
localities. In the United States, the Lake Superior region 
supplies very valuable ores; the Southern, Eastern, and 
Western States likewise produce immense quantities. In 
the Old World, Scandinavia, Elba, Great Britain, the 
Ural Mountains, and some other parts of Europe are 
famous iron-producing regions. 

Among the many ores of iron, space permits a descrip- 



276 iron. 

tion of only those varieties which are valuable to com- 
merce. 

1. Haematite, or Specular Ore, Fe 2 3 , occurs in veins, 
beds, and pockets. This ore is frequently of great purity, 
and is the ore chiefly employed in the reducing furnaces 
of the United States. 

It assumes different modifications, as : — 

(a) Amorphous Ore, a reddish, massive variety which 
resembles, in appearance, "iron rust." 

(6) Micaceous Ore, occurring in glittering scales. 

(c) Grranular Ore, of a crystalline structure. 

(d) Grape Ore, occurring in masses resembling bunches 
of grapes, and therefore frequently called botryoidal ore. 

,2. Brown Hcematite, Fe 2 3 + Fe 2 (OH) 6 , is frequently 
known as bog ore, and is the ore chiefly employed for 
reduction in France and Germany. 

3. Magnetite, or Loclestone, Fe 3 4 , is the well-known 
natural magnet ; it occurs in all the previously mentioned 
localities. A good quality of iron is obtained from this 
ore, but its reduction is somewhat difficult. 

4. Siderite, or Spathic Ore, is a carbonate of iron, FeC0 3 , 
containing also the carbonates of calcium, magnesium, 
and manganese. The renowned Styrian steel is manufac- 
tured from this ore at Erzberg. 

5. Argillaceous Ore, or Clay Iron-Stone, occurs in connec- 
tion with coal, and is the ore chiefly employed in England, 
This ore also occurs in Maryland, Pennsylvania, and Ohio. 

292. Preparation of Iron. — The reduction of iron as 
now carried on is one of the greatest industries of the age. 
In the primitive stages of this industry the process was a 
simple one which, however, permitted the employment of 
the purest ores only. . 



IRON. 



277 



A simple hearth was built with an opening at the 
bottom to admit a blast of air from a rude bellows, while 
another opening allowed the exit of the slag. After heat- 
ing the hearth, the ore and fuel were arranged in layers, 
and a continuous blast was maintained. In from four to 
six hours a porous " bloom " of iron weighing from 5 to 
30 lbs. was obtained. This "bloom" was then brought 
into the requisite shape by alternately heating and ham- 
mering it. Since the limits of our work prevent the 
giving of a consecutive history of the improvements on 
this method, it must suffice to say that the developments 
have been such that the present processes are applicable 
to any ore. 

The process now employed consists of two steps : — 



iron 



from 



(a) The production of cast 

the ore ; 
(5) The manufacture of wrought iron 

from cast iron. 

(a) The ore is first crushed and then 
mixed with crushed limestone and coal, 
when it is ready for the furnace. 

The best form of blast-furnace is 
shown in Fig. 19. This furnace, which 
is from 50 to 90 feet high, and from 14 
to 20 feet broad in its widest part, is 
constructed of masonry and has a lining 
of fire-brick. The whole stack is en- FlG - 19 - 

closed down to the point A in riveted iron boiler-plates. 
The masonry of the stack does not extend below A before 
the furnace is prepared to go into blast, but strong iron 
pillars (not shown in the cut) extend from that point to 
the ground. The hearth H consists of fire clay. It is 




278 iron. 

here that the molten metal collects. This hearth has twfi 
openings, the upper one for removing the slag, the lower 
one for drawing off the molten metal. The top of the 
stack D is funnel-shaped and is closed by an inverted 
cone, E, which lowers to admit the ore, fuel, etc., when 
the furnace is in operation, and which can be quickly 
raised again to close the opening. 

When a furnace is about to go into blast, the spaces H 
and B are filled with cord-wood, after which the whole 
portion below A, excepting the egress openings for the 
molten metal and slag, is enclosed by masonry ; a number 
of blow-pipes, or " Tuyeres," C, are also inserted, through 
which powerful blasts of air are to be driven. 

The wood is now ignited, the blast is started, and 
coal is introduced through the funnel D. When the 
interior of the furnace is sufficiently heated, the ore, mixed 
with coal and limestone, is admitted through D at regular 
intervals. 

Barring accidents, a furnace, after going into blast, runs 
night and day, shutting down but once or twice a year to 
renew the fire-brick linings and to make other needed 
repairs. 

The chemical changes which take place in the stack are 
not thoroughly understood, but the products obtained are 
cast iron, a glassy slag, carbon dioxide gas, carbon mon- 
oxide gas, hydrogen, and perhaps certain hydro-carbons, 
graphite, and cyanogen. The gases are not wasted, but 
are led through the pipe G — whose opening is seen at 
F — into burners situated under the boilers which supply 
steam to the engines used to drive the crushers, hoisters, 
air-condensers, etc., etc. 

The cast iron of the blast-furnace is not pure iron, but 
contains carbon and silicon, with traces of phosphorus, 



iron. 279 

arsenic, and sulphur, besides other metals in small quan- 
tities. 

(6) The second step is changing the cast iron into 
wrought iron. This is accomplished by the processes 
termed "refining" and "puddling," which consist in 
burning out the impurities and hammering the metal into 
coherence. The metal is then rolled into bars and sent to 
market. 

Another important branch of the iron industry is the 
manufacture of steel. 

Steel, in its chemical composition, stands midway 
between cast and wrought iron in the amount of carbon 
and silicon which it contains. It was formerly prepared 
at great expense by heating wrought iron in contact with 
carbon. The Bessemer process, however, has cheapened 
the production of steel, so that its use is becoming 
general. 

^his process is, briefly, as follows : — 

Cast iron is melted in a cupola furnace and run into 
an egg-shaped vessel called a " converter," which is so 
arranged that a blast of air may be driven up through 
the molten iron. 

In this way the carbon and silicon of the cast iron are 
burned out; then a sufficient quantity of pure molten cast 
iron is added to convert the whole into steel. In about 
half an hour from five to twelve tons of steel are thus 
obtained from one converter. 

293. Properties, Uses, and Salts of Iron. — Pure iron 
is a nearly silver-white metal, which rusts easily when 
exposed to dampness, ferric hydroxide and oxide being 
formed upon its surface. Iron is a very tenacious metal, 
and possesses the peculiar property of softening before it 
melts, thus allowing different pieces to be "welded." 



280 iron. 

The uses of iron and steel are so numerous and various 
that this age has well been termed the Iron Age. 

Exeecises. ^arae the uses of cast iron; wrought iron ; steel. What 
is meant by the " temper" of steel ? How is steel tempered % How is cast 
iron chilled ? What is malleable iron 1 How are twist gun-barrels made ? 
Laminated steel gun-barrels ? Damascus steel gun-barrels'? (Ask your 
gunsmith about the value and manufacture of gun-barrels.) How do cast 
iron, wrought iron, and steel differ in their properties 1 Can you "clinch" 
a common cut iron nail % Try it. Heat it red hot, cool it slowly, and then 
try. How can you draw the temper of a steel tool ? State the effects of 
magnets upon iron and steel. In what acids will iron dissolve ? Which 
acid is the best solvent ? (Try, at least, H 2 S0 4 , HNO y , HC1, and aqua 
regia.) What differences are there between the composition of cast iron, 
of wrought iron, and of steel ? 

Iron, like mercury (which see), forms two series of 
salts. Its compounds are numerous and important. Only 
a few of the most important ones can be given here. 

THE PRINCIPAL COMPOUNDS OF IRON APE : — 

(a) The Oxides, FeO, Fe 2 3 , and Fe 3 4 . The last two, 
which are ores of iron, have already been noticed. Ferric Hy- 
droxide, Fe 2 (OH) 6 , is a brownish precipitate obtained by adding 
ammonia to a cold solution of ferric chloride, Fe 2 Cl 6 ; this 
hydroxide is used in medicine. It is the group-reagent precipi- 
tate. The first oxide, FeO, is unimportant.- 

(b) Ferric Chloride, Fe Cl 3 . This salt is prepared by dis- 
solving iron wire in hydrochloric acid, after which the solution 
is thoroughly saturated with chlorine gas. It is used in medi- 
cine ; in the laboratory it is employed as a reagent. 

Ferrous Chloride, FeCl 2 , is prepared by dissolving iron wire 
in hydrochloric acid ; it is also used in medicine. 

(c) Ferrous Sulphate, Green Vitriol or Copperas, FeS0 4 + 
7 H a O. This salt is obtained when iron or ferrous sulphide is 
dissolved in sulphuric acid. It is used as a reagent and for 
preparing inks, dyes, and Prussian blue. Its uses as a deodor- 
ant and a disinfectant have alreadv been mentioned. 



IRON. 281 

(d) Ferrous Sulphide, FeS. This useful compound is made 
by stirring a portion of molten sulphur with a white-hot rod of 
wrought iron until the sulphur disappears. It is used in the 
laboratory for obtaining hydrogen sulphide. 

(e) Iron Pyrites, or FooVs Gold, FeS 2 , occurs native as yel- 
low, shining cubical crystals. It is found in various geological 
formations. Its principal use is for manufacturing sulphuric 
acid. 

Fe 2 S 3 probably occurs in magnetic pyrites. It can be pro- 
duced artificially, but is of small importance. 

(/) Potassium Ferrocyanide, or Yellow Prussiate of Potash, 
K 4 FeCy 6 . This salt is obtained by heating scrap iron in closed 
iron retorts with potash and animal matter such as hoofs, horns, 
hides, feathers, etc. 

This salt is of great importance, since it serves as the point 
of departure in the preparation of all the cyauogen compounds. 
In the laboratory it is used as a reagent for detecting iron. In 
the arts it is used for preparing Prussian blue, (Fe 2 ) 2 (FeCy 6 ) 3 
or Fe 7 Cy ]8 . This pigment is obtained when ferrous sulphate 
or ferric chloride is added to the ferrocyanide, K 4 FeCy 6 . 

(g) Potassium Ferri-cyanide, or Bed Prussiate of Potash, 
K 3 FeCy 6 , is obtained by oxidizing K 4 FeCy 6 by the action of 
chlorine. It is used to some extent as a reagent in the labora- 
tory. 

294. Tests for Iron. — 1. It is best to dissolve solids, 
and to test by 2. The blow-pipe tests are not satisfactory 
to beginners. 

2. Any solution is tested for iron by the reagents, 
potassium sulpho-cyanide, KCyS, and the ferro and ferri- 
cyanides, K 4 FeCv 6 and K 3 FeCy 6 . The change produced 
upon any solution depends upon whether the substance 
under examination contains a ferrous or a ferric salt, 
These changes are exhibited by the following table : — 



282 



CHROMIUM. 



Reagent. 



Ferric Salt. 



Ferrous Salt. 



KCyS 

K 4 FeCy 6 

(v 3 FeCj 6 



Red sol. [Fe 2 (CyS) 6 ] 
Deep blue prec. [Fe 4 (FeCy 6 ) 3 ] 
Xo prec. Reddish brown sol. 1 



No change. 

Pale blue prec. [K 2 Fe(FeCy 6 )] 

Deep blue prec. [Fe 3 (FeCy 6 ) 2 ] 



3. By employing a ferric salt (Fe Cl 3 ) and a ferrous 
salt (FeS0 4 ) as reagents, it is evident that the table given 
in 2 affords tests for Ferrocyanic and Ferricyanic acids or 
their derived salts. 

EXERCISES. 

1. Ignite in the Bunsen flame any ferrous salt, as FeS0 4 , on platinum 
foil. Try the residue with a magnet. Is it magnetic 1 What oxide of iron 
is thus obtained ? 

2. Heat any ferric salt, as Fe(N0 3 ) 3 , on charcoal in the reducing-flame. 
Do you obtain the same oxide as before ? 

3. Prepare, solid, FeCl 3 , and test for ferric salts. Write out a descrip- 
tion of the process, etc., in the form of an experiment. 

4. How can iron be prevented from rusting by "blueing" ; by paint- 
ing, etc. ; by coating with metals such as zinc, tin, copper, and nickel ? 

5. Try to precipitate a solution of FeS0 4 with NH 3 and NH^Cl. Acidu- 
late a fresh portion of the solution with HNG 3 ; boil, and try as before. 
Explain. 

CHROMIUM. 

Symbol, Cr'". — Atomic Weight, 52. — Specific Heat, 0.09975. 
— Melting-Point (higher than that of Platinum). 

295. Occurrence. — Chromium is a somewhat rare 
metal which never occurs free in nature. Its chief ores 
are Crocoisite, or chrome yellow, PbCr0 4 , and chrome iron- 
stone, Cr 2 3 (FeO). The color of many minerals is due to 
the presence of traces of the chromium compounds. 

296. Preparation. — Chromium is not employed in the 
metallic state. It is obtained for scientific purposes by 

^Tf the color is very dark, dilute the solution until you can see whether a "blue pre- 
cipitate is not also formed. In such a case, you have both the ferric and ferrous salt* 
present. 



CHKOMIUM. 283 

mixing its oxide with sugar, after which the mixture is 
strongly heated in a lime crucible. Thus obtained, it is a 
gray, crystalline powder. 

297. Properties, Uses, and Compounds of Chromium, 

— Metallic chromium presents a crystalline, silvery ap- 
pearance under the microscope. Its principal use is to 
harden steel, to which it imparts a superior hardness. 

The best working solutions for chromium are solutions of 
chromous chloride, CrCl 2 ; chrome alum ; potassium cliro* 
mates; or the acid chr ornate.. Metallic chromium is solu- 
ble in hydrochloric acid, CrCl 2 being obtained. 

THE PRINCIPAL CHROMIUM COMPOUNDS ARE: — 

(a) The Oxides, Cr 2 3 and Cr0 3 . Chromic oxide, Cr 2 3 , is 
used in coloring glass and enamel green. It is obtained by 
fusing potassium bichromate, K 2 Cr 2 7 , with sulphur or with 
ammonium chloride, after which the fused mass is treated with 
water. The oxide Cr0 3 may be regarded as the anhydride of the 
hypothetical chromic acid, H 2 Cr0 4 : H 2 + Cr0 3 = H 2 Cr0 4 . 

Chromic Hydroxide, Cr (OH) 3 , is the group-reagent precipi- 
tate obtained by adding ammonia and ammonium chloride to 
the solution of a salt in which chromium is combined as a base. 

Guignet's Green, Cr 2 0(OH) 4 , is now largely used as a pig- 
ment ; it is sold in drug stores under the name chrome green. 
This pigment is prepared by fusing potassium bichromate mixed 
with crystallized boric acid in quantities proportional to the 
molecular weights of the substances employed. The fused 
mass is then ground to a fine powder. 

(b) Potassium Chromium Sulphate, or Chrome Alum, 
K 2 Cr 2 (S0 4 ) 4 + 24H 2 0. This salt is obtained as a by-product 
in the manufacture of alizarine and in many other oxidations. 
It is used in dyeing, tanning, and in calico printing. 

(c) Potassium Chromate, K 2 Cr0 4 . This salt is obtained by 



284 CHROMIUM. 

adding potassium hydroxide to a solution of potassium bichro- 
mate. It is used in the laboratory as a reagent. 

(d) Potassium Bichromate, K 2 Cr 2 7 , or Add Potassium 
Chromate. This is an important salt obtained from chrome 
iron ore by three steps : (1) Eoasting the ore to oxidize it; 

(2) fusing the roasted ore with lime and potassium carbonate ; 

(3) lixiviating the fused mass with as little water as possible, 
and then treating the liquor with sulphuric acid. This salt is 
used to prepare chrome yellow, PbCr0 4 , to dye wool, and to 
prepare other chromium compounds. It is also used in the auto- 
type process and as a reagent. 

The relation between potassium chromate and bichromate 
may be understood best by considering the acids from which 
they are derived. Hypothetical chromic acid probably has the 
composition H 2 Cr0 4 . Its normal potassium salt is K 2 Cr0 4 . If we 
imagine chromic acid to lose water according to this equation, — 

2 H 2 Cr0 4 - H 2 = H 2 Cr 2 7 , 
we have left the acid from which potassium bichromate, K 2 Cr 2 7 , 
is derived, bichromic or pyrochromic acid. 

Query. Are there any similar relations met with in connection with 
sulphur compounds ? Compare carefully sulphuric and chromic acids. 

(e) Lead Chromate, or Chrome Yelloiv, PbCr0 4 . This com- 
pound occurs in nature as crocoisite, and is also prepared 
artificially by precipitating a lead salt with potassium bichro- 
mate ; used in calico printing and as a pigment. Chrome Red. 
Pb 2 Cr0 5 , and Chrome Orange, a mixture of chrome red and 
chrome yellow, are much used as paints. 

The following peculiarities will be noticed concerning 
the chromium compounds : As a base it forms the chro- 
mous and chromic salts, of which chromous chloride, CrCl 2 , 
and chromic chloride, Cr Cl 3 , may be taken as examples. 
As an acid-forming element, it gives rise to three series 
of salts, — the chromites, chromates, and the bichromates, 



CHROMIUM. 286 

of these, ferrous chromite, FeCr 2 4 , lead chromate, PbCrO^ 
and' potassium bichromate, KoCr 2 7 , may be taken as 
representatives. 

Note. As the chromates do not yield precipitates with NH 3 and 
NH 4 C1, it is advisable to use a salt like chrome alum, in which chromium 
is a base, for the solution which the beginner is to analyze for the third 
group metals. The use of HC1 and H. 2 S may then be dispensed with. 

298. Tests for Chromium. — - 1. Chromium, free or in 
compounds, gives the borax or microcosmic bead an 
emerald-green color. 

2. Fuse the substance to be tested on platinum foil or 
porcelain with KNO, and Na 2 C0 3 . These reagents will 
oxidize any chromium present to a chromate. Now dis- 
solve the yellow mass in water, acidify with acetic acid, 
and add lead acetate ; a dense yellow precipitate, PbCr0 4 , 
indicates chromium. 

3. A chromate or a bichromate may be recognized by 
adding : — 

(a) H 2 S, when the color changes to green. 

(5) Lead acetate, which gives yelloiv lead chromate, 
PbCr0 4 . 

(<?) Silver nitrate, which gives brownish-r^cZ silver 
chromate, Ag 2 Cr0 4 . 

Note. Potassium chromate is a yellow crystalline solid, while the 
bichromate is of a red color. 



EXERCISES. 

1. Prepare (and describe its preparation as an experiment) Cr 2 3 . 

2. Similarly prepare and describe Guismet's green. 

3. Likewise prepare and describe K 2 CrG 4 and chrome yellow. 

4. Try to precipitate a chromate with NH 3 and NH 4 C1. Acidulate with 
HC1 a fresh portion of chromate, pass H 2 S, and try the same precipitante. 
What results 1 Warm a chromate with (NHJ 2 S. What results 



286 ALUMINUM. 



ALUMINUM. 



Symbol, Al'". — Atomic Weight, 27. — Specific Heat, 
0.2140. — Melting-point, 700° C. 

299. Occurrence. — Next to oxygen and silicon, alu- 
minum is the most plentiful and widely-occurring ele- 
ment. It is the basis of all clayey soils, and occurs as 
feldspar or K 2 Al 2 Si 6 Oi6 in granite, gneiss, syenite, trachite, 
porphyn r , etc. 

Albite, a sodium feldspar, also occurs in large quan- 
tities. Kaolin, or porcelain clay and china clay, is feld- 
spar which has been disintegrated and decomposed by 
exposure to the atmosphere. 

The different varieties of garnet, mica, and slate stones 
are important silicates of aluminum and other metals. 
Alumina or aluminum oxide, A1 2 3 , is known as corun- 
dum or emery when coarse, but when crystallized it con- 
stitutes the important jewels sapphire, rub} T , oriental 
emerald, oriental topaz, and oriental amethyst. 

300. Preparation. — Metallic aluminum is prepared 
from bauxite, Al 2 Fe 2 O s H 4 . 

From this substance the oxide of aluminum, A1 2 3 , is 
first prepared thus : The bauxite is heated with soda in a 
reverberatory furnace, when a soluble compound of sodium 
and aluminum is formed; this compound is dissolved in 
water, and a current of carbon dioxide passed through the 
solution, precipitating the required alumina. 

This oxide is then mixed with charcoal and sodium 
chloride and heated to a white heat ; then chlorine gas is 
passed through the mixture, thus forming a volatile double 



ALUMINUM. 287 

chloride of aluminum and sodium, from which the metal 
is obtained by fusing with metallic sodium and cryolite. 

Aluminum is now cheaply and almost entirely obtained 
directly from the oxide, A1 2 3 , by reduction with carbon, 
in the absence of air, in an electric circuit. 

301. Properties, Uses, and Salts of Aluminum. — 
Aluminum is a white, malleable metal which does not tar- 
nish or oxidize under ordinary'circumstances. Its extreme 
lightness (sp. gray. = 2.67), elasticity, tenacity, and the 
fact that it is not easily oxidized fit it for many uses which 
the cost of its production alone prevents. It is chiefly 
employed at present in making philosophical instruments. 
Aluminum forms valuable alloys with copper and silver. 

The best solvent for aluminum is hydrochloric acid, 

THE PRINCIPAL COMPOUNDS OF ALUMINUM NOT PREVI- 
OUSLY MENTIONED ARE: — - 

(a) Sodium Aluminate, Na 2 Al 2 4 , obtained by fusing bauxite 
with sodium sulphate and carbon ; it is used as a mordant in 
dyeing and calico printing, for preparing colored lakes, and 
for sizing paper. 

(b) Aluminum Sulphate, A1 2 (S0 4 ) 3 . This is used in immense 
quantities as a mordant and for weighting paper, and is obtained 
by roasting kaolin, which is then dissolved in sulphuric acid, and 
the solution evaporated till it will solidify when cool. 

(c) The Alums, of which there are many. We give the 
formulae of the most important : K 2 A1 2 (S0 4 ) 4 + 24 H 2 ; 
Ag 2 Al 2 (S0 4 ) 4 + 24 H 2 ; and (NH 4 ) 2 A1 2 (S0 4 ) 4 + 24 H 2 0. 

(d) Aluminum Hydroxide, Al (OH) 3 , obtained by adding 
ammonia to a soluble salt of aluminum ; it is the white, gelati- 
nous group-reagent precipitate. 

(e) Phosphates of Aluminum. The principal one is tur- 
quois, a well-known jewel, which owes its bluish or greenish 



288 ALUMINUM. 

color to the presence of copper. Its formula is Ai 2 P0 4 (OH) 3 + 
H 2 ; the ancient gem was cut from odontolite, a fossil tooth or 
bone. 

(/) Silicates of Aluminum. The principal ones are : — 

Topaz, Al 2 F 2 Si0 4 . A yellowish-colored jewel whose coarser 
forms are frequently used instead of emery for polishing purposes. 

Beryl, Al 2 Be 3 Si 6 18 . A green variety, the true emerald, is 
used in jewelry. What is the u oriental emerald?" 

Lapis Lazuli, a bluish mineral of unknown chemical con- 
stitution containing silicates of aluminum and sodium, besides 
sulphur. It is used for ornamental purposes, and when pow- 
dered is known as idtramarine, a valuable paint. The best 
ultramarine is now manufactured in large quantities by fusing 
together a very fine variety of clay, sand, sulphur, and resin. 

302. Tests for Aluminum. — 1. Solids are fused with 
Na 2 C0 3 or HKS0 4 and then dissolved in hydrochloric acid. 
This solution is treated as in 

2. Add an excess of NH 4 C1 and ammonia to the solu- 
tion. Aluminum gives a white, gelatinous precipitate, 
Al (OH) 3 . 

3. The solution may be tested further by adding to 
another portion : — 

(a) Na 2 C0 3 , — -the precipitate, Al (OH) 3 ; 
(5) Na 2 HP0 4 , — a white precipitate, A1P0 4 , soluble 
in KOH, insoluble in acetic acid. 

EXERCISES. 

1. Obtain at your druggist's different kinds of alum, and determine what 
bases are present. 

2. For a valuable paper on alum as a purifier for drinking-water, see 
the "Chemical News," May 22, 1885, p. 241. 

3. Does aluminum act both as a base and an acid-forming element ? 

4. Ask your jeweller to show you specimens of turquois, beryl, topaz 
ruby, sapphire, emerald, and lapis lazuli. How do their values compare ? 

5. Examine baking powder for alum. 



ALUMINUM. 289 

303. To separate and identify Iron, Chromium, and 
Aluminum. — From the solution remove the first and 
second group metals (if any be present) by means of HC1 
and H 2 S. Boil the filtrate (if HC1 and H 2 S were em- 
ployed) to expel all the hydrogen sulphide. If any iron 
salts be present, they are now in the ferrous condition; 
therefore add a little nitric acid, and boil a short time to 
oxidize the ferrous to ferric salts. The solution is now 
prepared for the following treatment : — 

1. Add ammonia till the solution is alkaline, and then 
add ammonium chloride ; the precipitate obtained may be 
any or all of the hydroxides, Fe (0H) 3 , Cr (0H) 3 , 
Al (0H) 3 . Filter and wash the precipitate. 

2. Pierce the point of the filter-paper, and wash the pre- 
cipitate through into a beaker-glass ; add potassium or 
sodium hydroxide, and boil for several minutes. The 
hydroxides of iron and chromium remain unchanged, 
while the aluminum is dissolved. Now filter the contents 
of the beaker, and treat the precipitate for iron and 
chromium as in 3 and 4. Treat the filtrate for aluminum 
as in 5. 

3. Dissolve a portion of the precipitate in HC1, and test 
for iron as in 294, 2. If iron be present, test a portion of 
the original solution to determine if the salt be in the fer 
rous or ferric condition. 

4. Fuse on platinum foil a second portion of the same 
precipitate with sodium carbonate and potassium nitrate 
Any chromium present is thus oxidized to a chromate. 
Dissolve the fused mass in water, and test by 298, 3. 
Test the original solution for chromates. 

Note. If the original solution contained chromates, they would be re 
duced by H 2 S to salts in which chromium would give a precipitate with 
NH 4 C1 and NH 3 . If no first and second group metals were present, and 



290 NICKEL. 

HC1 and H 2 S were not employer!, it would be necessary to test the original 
solution (unless it is colorless) directly for cliromates, since chromates 
do not give Cr(OH) 3 with NH 3 and NH 4 C1. In case the solution con- 
tains the salts of the metals of division B or those of the fourth group, it 
is necessary to use HC1 and H 2 S. 

5. To the filtrate from 2 add sufficient hydrochloric 
acid barely to acidify it ; then add ammonia ; a white 
precipitate, Al(OH) 3 , identifies aluminum. 

Sug. Explain the significance of these equations : — 

(1) 2 H 2 Cr0 4 + 6 HC1 + 3 H 2 S = 2 CrCl 3 + 3 S + 8 H 2 0. 

(2) 2 Fe" + 8 HN0 3 = 2 Fe"'(N0 3 ) 3 + 2 NO + 4 H 2 0. 

hot 

(3) 2 Fe"'(N0 3 ) 3 + H 2 S = 2 Fe"(N0 3 ) 2 + 2 HN0 3 + S. 
Which equation shows the transformation of chromium in a chromate 

to chromium as a base ? Which equation shows the change of iron from 
the ferric to the ferrous condition ? 



NICKEL. 

Symbol, Ni". — Atomic Weight, 58.7. — Specific Heat> 
0.1080. — Melting-Point, nearly a white heat. 

304. Occurrence. — Nickel never occurs native, but its 
ores are usually found in connection with cobalt ores. 
Meteoric iron always contains nickel. Its chief ores are 
Kupfer-nickel, Ni As, — which is the most important ore, 
and which is found in Saxony, Styria, and the United 
States, — Nickel-glance, Ni(AsS) 2 ; Breithauptite, NiSb ; 
Nickel-blende, NiS. (Also see Cobalt.) 

305. Preparation, — Metallic nickel is now obtained 
mostly in the wet way. The ores are roasted, and then 
dissolved in hydrochloric acid ; this solution usually con- 
tains iron, cobalt, and copper, which accompany the nickel 
in its ores. In such cases the iron salts are oxidized by 
chlorine and then precipitated by adding limestone ; the 



NICKEL. 291 

copper is precipitated by hydrogen sulphide and the cobalt 
by bleaching-powder. The remaining clear solution con- 
tains the nickel, which is now precipitated by the addition 
of an alkali, usually sodium hydroxide. From the nickel 
hydroxide thus obtained the nickel is reduced by fusion 
with charcoal. 

306. Properties, Uses, and Salts of Nickel. — Nickel is 
a white, hard metal, scarcely tarnishing in the air, and 
susceptible of a brilliant polish. It is accordingly used 
extensively in coinage and in plating other metals. The 
salt used in electro-plating is a double sulphate of nickel 
and ammonium. Its chief alloy is German silver. 

SuG. For a valuable paper on Electro-Nickel Plating as an Industry, 

which gives the history and development of the details of the processes 

employed in electro-nickel plating, see " Scientific American Supplement' 5 
for May 10, 1884, p. 6957. 

Nickel, like iron, can be welded, and is likewise at- 
tracted by the magnet. 

The lest solvent for nickel is dilute nitric acid, 

THE PRINCIPAL COMPOUNDS OF NICKEL ARE : — 

(a) The Oxides, NiO and NLO s . We must also note the 
apple-green hydroxide, Ni(OH) 2 , which maybe obtained by the 
action of an alkali, as NaOH, on a solution of a nickel salt. 

(b) Nickel Sulphate, NiS0 4 -h 7 H 2 0. Prepared by dissolv- 
ing the metal or its hydroxide in sulphuric acid. 

(c) Nickel Ammonium Sulphate, Ni(NH 4 ) 2 (S0 4 ) 2 + G H 2 0. 
Obtained by adding ammonium sulphate to nickel sulphate. 

(d) Nickel Sulphide, NiS. Obtained as a black powder by 
adding ammonium sulphide to an alkaline solution of a nickel 
salt. It is the group-reagent precipitate ; it also occurs in na- 
ture as Millerite in rhombohedral or capillary crystals. 

307. Tests for Nickel. — 1. Nickel compounds in the 



292 COBALT. 

oxidizing-fi'ame give the borax bead a brownish-red color 
when hot, yellow when cold. In the reducing-Qsune the 
bead assumes a grayish color owing to the reduction of 
metallic nickel. The presence of cobalt may obscure this 
test. See 

2. In the wet way the solid is dissolved in water or aqua 
regia. This solution is then tested for nickel thus : — 

(a) With a drop or two of ammonia the apple-green 
hydroxide, Ni(OH) 2 , is thrown down ; but if ammonia be 
added to excess, the hydroxide dissolves, forming a blue 
solution. Again add potassium hydroxide to this blue so- 
lution, and the apple-green precipitate again appears. 

(5) Add potassium or sodium hydroxide to the original 
solution, — an apple-green precipitate. In general, all the 
salts of nickel are greenish. 

EXERCISES. 

1. Dissolve a nickel three-cent piece in nitric acid, and determine what 
metals the coin contains. 

2. Heat a nickel salt with Na 2 C0 3 on charcoal. Does a magnet attract 
the powder obtained'? What other substance (metallic oxide) is thus 
attracted ? 

3. Read R. & S., Vol. II., Pt, II., pp. 146-149, on the alloys of nickel. 
Prepare M(N0 3 ) 2 and NiS0 4 , and describe the processes, etc., as ex- 
periments. 

COBALT. 

Symbol, Co". — Atomic Weight, 59.5. — Specific Heat ; 
0.10674. — Melting-Point, a white heat. 

308. Occurrence. — Cobalt does not occur free, and its 
ores are neither plentiful nor widely distributed. Some of 
its ores are Speiss Cobalt, Co(Ni,Fe)As 2 ; Skutterrudite. 
CoAs 3 ; and Cobalt-glance, CoFeAs 2 S 2 . 



COBALT. 293 

309. Preparation. — Metallic cobalt is of little or no 

use in the arts, and is prepared in small quantities only 
for scientific purposes. The metal is reduced by strongly 
heating the oxide or chloride of cobalt in an atmosphere 
of hydrogen, when the cobalt is obtained as a gray, metal- 
lic powder. 

The metal can also be obtained in a coherent state by 
fusing its oxalate under a layer of powdered glass and 
afterwards fusing the metal in a graphite crucible. 

310. Properties and Compounds of Cobalt. — Coherent 
metallic cobalt resembles iron in its whitish color and in 
being attracted by the magnet. It oxidizes but slowly 
when in the coherent condition, but when in the form of 
a powder it oxidizes quickly at ordinary temperatures. 

The compounds of cobalt are valuable, and are prepared 
directly from the arsenical ores, preferably speiss cobalt, 
Co(Ni,Fe)As 2 . 

The ore is roasted to vaporize the arsenic, then fused 
with lime and sand to remove the iron. The residue is 
now dissolved in hydrochloric acid, and any remaining 
impurities are precipitated by adding successively chlorine 
calcium carbonate, and hydrogen sulphide. The remaining 
solution is thus freed from all the first and second group 
metals, the cobalt only remaining in solution. 

The oxide of cobalt is obtained from this solution by 
the aid of bleaching-powder. The oxide is an article of 
commerce, and is used for coloring glass blue, and for pre- 
paring the salts and compounds of cobalt, which are of 
great value as pigments. 

There are two series of cobalt salts, — the cobaltous and 
cobaltic. In the latter series, the salts are of a varying 
formula, and not of sufficient importance to warrant a 



294 COBALT. 

notice here. The cobalt salts are violet when anhydrous, 
and pink in color when hydrated ; hence they are used 
to make " sympathetic ink," which becomes visible upon 
warming. 

Cobalt or its oxides, OoO and Co 2 3 , are soluble in dilute 
HNOs. 

THE PRINCIPAL COBALT SALTS ARE: 

(a) Cobaltous Chloride, CoCl 2 . Prepared by dissolving the 
metal or its carbonate in hydrochloric acid ; it is used as a 
sympathetic ink. 

(b) Cobaltous Nitrate, Co(N0 3 ) 2 . Prepared by dissolving 
the metal or its carbonate in dilute nitric acid ; it is used as a 
reagent. 

(c) Cobaltous Sulphide, CoS, the group-reagent precipitate. 
A black precipitate obtained by adding ammonium sulphide to 
a solution of a cobalt salt. 

(d) Silicates of Cobalt. These are prepared artificially, and 
are known as " Smalt." The ore is first roasted sufficiently to 
oxidize the cobalt, and then fused with quartz and potash, 
when a dark-blue glass is formed, which is crushed into dust, 
under water, by granite millstones, and is sold as a pigment. 

(e) Rinmann's Green. A pigment prepared by precipitating 
a solution of zinc and cobalt sulphates by sodium hydroxide. 
This precipitate is then heated and reduced to an impalpable 
powder. Its formula is unknown. 

(/) Thenar -d's Blue, or Cobalt Ultramarine. A valuable 
pigment prepared by heating alumina with a cobalt salt. Its 
formula varies. 

311. Tests for Cobalt. — 1. Any cobalt compound 
colors the borax or microcosmic bead blue, — often appear- 
ing black when the cobalt is in excess ; when powdered, 
the dust obtained from the bead is blue in all cases. 



MANGANESE. 295 

Note. Should iron or nickel compounds be present, they may be 
reduced to a colorless condition (metallic) by the continued application of 
the reducing-flame, so that they will not interfere with this test. 

312. To separate and identify Xickel and Cobalt. — 

To a somewhat concentrated solution of the salts of these 
two metals add acetic acid and potassium nitrite (KX0 2 ). 
Warm the solution gently for some time, and allow it to 
stand for about twenty-four hours. At the end of this 
time a yellow, crystalline precipitate of potassium-cobaltic 
nitrite will settle. 

(a) Obtain the nickel test from the solution. (Art. 307.) 
(5) Apply the cobalt test (Art. 311) to the precipi- 
tate. 

Suo. Eead the " Chemical Xews " for April 10, 1885, p. 170, for a ne^v 
method of separating nickel and cobalt. 

MANGANESE. 

Symbol, Mn". — Atomic TTeioht. 55. — Specific Heat, 
0.1217. — Meltixg-Poixt, a white heat. 

313. Occurrence. ■ — ■ Manganese never occurs free. Its 
chief ore is Pyrolusite, MnO a ; it also occurs in Braun- 
ite, Mn 2 O s , Hausmannite, Mn 3 4 , Rhodocrosite, MnC0 3 , 
and Manganite, Mno0 2 (OH) 2 . 

314. Preparation. — Metallic manganese is not em- 
ployed for practical purposes. It is obtained by fusing, 
at a white heat, a mixture of any one of its oxides and 
charcoal in a closed crucible lined with graphite. 

315. Properties and Compounds of 3Ianganese. — 

Manganese is a reddish-white, brittle metal, oxidizing so 
easily in the air that it must be kept under naphtha oi 
coal-oil. 



296 MANGANESE. 

THE IMPORTANT COMPOUNDS OF MANGANESE ARE : — 

(a) The Oxides. — Manganous Oxide, MnO. A grayish- 
green powder. 

Mangano so -Manganic Oxide, or Red Oxide of Manganese, 
Mn 3 4 . This substance crystallizes in acute, quadratic pyra- 
mids. 

Manganic Oxide, Mn 2 3 - This oxide is brownish-black, and 
crystallizes in obtuse quadratic pyramids. As it occurs in 
nature it is known as Braunite. 

Manganese Dioxide, or Black Oxide of Manganese, Mn0 2 . 
This is the most important of the manganese oxides. It is used 
in the laboratory in many ways, but its principal use is for pre- 
paring chlorine gas, thus : — 

Mn0 2 + 4 HC1 = MnCl 2 + 2 H 2 + Cl 2 . 

The chloride, MnCl 2 , is not a waste product, since it may be 
again converted into the dioxide : — 

(1) MnCl 2 + CaCOo = MnC0 3 + CaCl 2 ; 

(2) MnC0 3 + O (heated in a blast of hot air) = Mn0 2 + C0 2 . 

This illustrates a process employed in generating chlorine for 
the manufacture of bleaching- powder. 

Manganese Heptoxide, Mn 2 7 , is a dark, reddish-brown liquid, 
which yields, with water, permanganic acid : Mn 2 7 + H 2 = 
2 HMn0 4 . 

The other oxides of manganese are basic oxides ; of these 
MnO is the strongest base. 

(b) Manganic Acid, H 2 Mn0 4 , and Permanganic Acid. 
HMn0 4 . The first is a very unstable acid not known in the 
free state ; its salts, the manganates, are green in color, and 
very unstable, except in the presence of an excess of alkali. 

Permanganic acid is prepared thus : — ■ 

Ba(Mn0 4 ) 2 + H 2 S0 4 = 2 HMn0 4 + BaS0 4 . . 
This acid in aqueous solution is a deep-red liquid possessing 



MANGANESE. 297 

a bitter, metallic taste ; it is readily decomposed by heat or 
exposure to light. Of its salts the principal one is 

Potassium Permanganate , KMn0 4 or K 2 Mn 2 8 . This is a 
crystalline substance, the color of which varies through green, 
black, and steel-blue, depending upon the age and exposure of 
the crystals. The uses of the permanganate are numerous, 
with many of which the student is already acquainted. Organic 
substances, as in drinking-water, reduce permanganates to lower 
compounds, partially manganates. 

Condy's Disinfecting Liquid is obtained by dissolving the 
permanganate in water. The commercial article, however, is 
not a pure permanganate, and is prepared on the large scale 
by heating to redness for several hours caustic soda with man- 
ganese dioxide ; the fused substance is then lixiviated with 
water, and the solution is afterwards concentrated, when it is 
ready for the market. 

Exp. 163 t. Chameleon Mineral is a remarkable compound 
which may be readily prepared as follows : Fuse in a crucible 
equal weights of solid potassium hydroxide and finely levi- 
gated manganese dioxide. Fill a tall jar with pure water, and 
slowly drop in the powdered and cooled mass formed by fusion. 
Note the colors obtained as the fine particles find their way to 
the bottom of the vessel. 

Note. The chemical changes which take place in this experiment are, 

first, the formation of a salt of the composition KgMnO^ potassium man- 

ganate, 

3 Mn0 2 + 2 KOH = K,Mn0 4 + Mn 2 3 + H 2 0, 

the solution of which is green. This salt is unstable unless free alkali is 
present. When poured into water it is converted into the permanganate, 
K 2 Mn 2 8 (or KMn0 4 ), the solution of which has a beautiful purplish-red 
color. Hence, in the above experiments, the color changes from green to 
purplish-red, and various intermediate colors are observed. 

(c) Manganese Sulphide, MnS, is the flesh-colored group-re- 
agent precipitate obtained by ammonium sulphide in an alkaline 
solution of any salt of manganese. It also occurs as the rnin- 



298 zinc. 

eral Alabandite, or Manganese Blende, in cubical or octahedral, 
steel-gray crystals. 

316. Tests for Manganese. — 1. To the borax and 
microcosm ic beads in the oxidizing-flame manganese gives 
a violet color when hot, amethyst-red when cold. 

In the reducing-flame the bead becomes colorless. 

2. When fused on platinum foil with Na 2 C0 3 and 
KN0 3 , manganese compounds give a bright-green mass, 
(what?). Dissolve this mass in water and add HN0 3 ; a 
red solution is formed. 

3. The manganese acids may be distinguished by the 
color of their salts in solution, and by further yielding 
the reactions in 1 and 2. 

What substances bleach a permanganate ? 



ZINC. 

Symbol, Zn". — Atomic Weight, 65.3. — Specific Heat, 
0.0955.— Melting-Point, 423° C. 

317. Occurrence. — Zinc seldom or never occurs native. 
Its chief ore is Smithsonite, or Z11CO3. Franklinite, 
(Zn, Fe)0 + Fe 2 3 ; Zinc blende, ZnS ; Willeinite, Zn 2 Si0 4 , 
and a red oxide which owes its color to a reddish oxide 
of manganese, are the ores chiefly employed in the reduc- 
tion of zinc in the United States. 

318. Preparation. — The ores of zinc are first roasted 
and ground fine, then mixed with coal dust to the amount 
of one-half their weight. This mixture is then placed in 
clay retorts, and heated until the zinc is reduced and 
vaporized, when the escaping vapors are condensed in iron 



zinc. 299 

condensers. Zinc thus prepared is the commercial article, 
and is seldom pure, since it contains small quantities of 
carbon and iron, lead, arsenic, antimony, and other metals. 

319. Properties, Uses, and Salts of Zinc. — Zinc is a 
malleable, ductile, bluish-white metal which is used for 
many purposes. Its uses in our dwellings are familiar to 
all. It is also used, when alloyed with copper to form 
brass, in ways innumerable. In the laboratory, zinc is 
used in batteries, in preparing hydrogen, in desilvering 
lead, and in reducing other metals from their solutions. 
Sheet iron, when covered with a coating of zinc, is said to 
be galvanized. 

Sug. Let the student name the metals which he can obtain from solu- 
tions of their salts by suspending a strip of zinc therein. 

In the form cf dust, zinc is used in chemistry as a reduc- 
ing agent. Zinc-dust burns in the Bunsen flame with a 
white bluish light. 

Pare zinc dissolves very slowly in sulphuric acid, hence 
it is well to add a small quantity of platinum chloride to 
the granulated zinc employed by the student. Cover the 
zinc with water, pour in the platinum chloride, and a coat- 
ing of platinum black is soon deposited on the zinc. Now, 
when the sulphuric acid is poured in, a galvanic current is 
established, and the zinc readily dissolves. A solution of 
pure copper sulphate answers the same purpose. 

Zinc salts, when taken internally, are poisonous. Canned 
goods may become poisonous when the tin cans are sol- 
dered by the aid of zinc chloride, which is a soldering fluid 
often employed by tinners. 

Sug. Head the " Chemical News/' June 5, 1885, p. 268, for valuable 
information concerning poisoned canned goods. 



300 zinc. 



THE PRINCIPAL COMPOUNDS OF ZINC ABE; 

(a) Zinc White, ZnO. Used as a paint. 

(6) Zinc Chloride, ZnCl 2 . Used as a caustic in surgery, 
and in organic chemistry for removing the elements of water 
from many substances. It is also used in " weighting" cotton 
goods. 

(c) Zinc Sulphate, or White Vitriol, ZnS0 4 + 7 H 2 0. Used 
in medicine and in dyeing. 

(d) Zinc Sidphide, ZnS, the group-reagent precipitate (white) . 

320. Tests for Zinc. — 1. Unknown solids are tested 
for zinc by the blowpipe. When heated in the oxidizing 
flame on charcoal, zinc compounds with Na 2 C0 3 give a 
coating around the assay, which is yellow when hot, white 
when cold. 

2. If after being treated as in 1, the mass be moistened 
with cobaltous nitrate and- heated again, it turns green. 
This color is a beautiful one, known as Rinman's green. 

3. Solutions are first made alkaline, and ZnS (white) is 
precipitated with (NH 4 ) 2 S. This sulphide is insoluble in 
dilute acetic acid, and is further tested by 1 and 2. 

321. To separate and identify Nickel, Cobalt, Man- 
ganese, and Zinc. — Obtain the precipitates MS, CoS, MnS, 
and ZnS, as directed in Art. 290. Warm the test-tube 
containing the precipitate until the sulphides settle ; then 
filter out and wash this precipitate and wash it through 
into a test-tube ; dissolve as much of it as possible with 
cold dilute HC1. Any residue may be NiS or CoS, or 
both; filter and test as in (a). The filtrate is tested by 
(J) for manganese and zinc. 

(a) This residue is always black when containing Ni or 



REACTIONS IN GROUP III. 301 

Co, or both metals. Test it by the borax bead. (See 
Arts. 307, 1 and 2, and 311, 1, note.) It is well, also, to 
proceed by 312 to make sure whether both are present. 

Note. Some free sulphur usually remains on the paper with thir 
residue. Whence came it ? 

(J) Boil to expel H 2 S, and add a decided excess of KOH 
to the hydrochloric acid solution in a test-tube. Allow it 
to stand some time, and shake it frequently. If manga- 
nese be present, it will be precipitated as Mn(OH) 2 , when 
it must be filtered out, and tested by Art. 316, 2. 

Note. Test this precipitate also for Ni and Co, since the HC1 is apt to 
dissolve small portions of their sulphides. 

For detecting the zinc, acidify with acetic acid the fil- 
trate just obtained, and add (XH 4 ) 2 S, — a white precipitate, 
ZnS. Also test by Art. 320, 1 and 2. 

General Note. Phosphoric acid or phosphates, when present in third 
and fourth group solutions, cause them both to be precipitated with 
(XH J 2 S. For separation of third and fourth group metals in presence of 
phosphates, see Douglas and Prescott's " Qual. Anal.," p. 241. 

SOME REACTIOXS IN GPvOUP III. 

Balance and explain these equations : — 

(1) Fe + H 2 S0 4 = FeS0 4 +H. 

(2) Fe + (cold dil.) HX0 3 = Fe(X0 3 ), + NH 4 M) 3 + H 2 0. 

(3) Fe + (hot dil.) HX0 3 = Fe(X0 3 ) 3 + NO + H 2 0. 

(4) Fe + HC1 = FeCl 2 + H. 

(5) FeCl 2 + CI = FeCl 3 . 

(6) FeS0 4 + H 2 S0 4 (boiling) = Fe 2 (S0 4 ) 3 + S0 2 '+ H 2 0. 

(7) FeCl 3 + H 2 S = FeCl 2 -f HC1 + S. 

(8) FeS0 4 + (NH 4 ) 2 S = FeS + (NH 4 ) 2 S0 4 . 

(9) FeCl 3 + KOH = Fe(OH) 3 + KC1. 
(10) Al + H 2 S0 4 = A1 2 (S0 4 ) 3 + H. 



302 



THE RAKE METALS OF GROUP III. 



(11 
(12 

(13 

(14 

(15 

(16 

(17 
(18 
(19 

(20 
(21 
(22 
(23 
(24 
(25 
(26 
(27 



Al + HC1 = A1 2 C1 6 + H. 

Al Cl 3 + (NH 4 ) 2 S + H 2 = AyOHJs + NH 4 C1 + H 2 S. 

K 2 Cr 2 7 + (NH 4 ) 2 S 2 + H 2 = Cr (OH), + K 2 S0 3 + NH 3 + S, 

Mn0 2 + HC1 = MnCLj + CI + H 2 0. 

Mn0 2 + H 2 S0 4 + NaCl = MnS0 4 + Na 2 S0 4 + Cl 2 + H 2 0. 

MnS0 4 + (^ T HJ 2 S = MnS + (NHJ 2 S0 4 . 

Co + HNOg = Co(N0 3 ) 2 + H 2 + NO. 

CoN0 3 + (NH 4 ) 2 S = CoS + (NHJNOg. 

CoCl 2 + KN0 2 + HC 2 H 3 2 + H 2 = (KNQ 2 ) B , Co 2 Q(NQ 2 )„ 

H 2 + KC1 + NO + KC 2 H 3 2 . 
Ni + HC1 = NiCl 2 + H. 
m + HNOg = Ni(N0 3 ) 2 + H 2 + NO. 
MC1 2 + (NH 4 ) 2 S = NiS + NH 4 C1. 
MC1 2 + KOH = Ni(OH) 2 + KC1. 
Zn+H 2 S0 4 =ZnS0 4 +H. 
Zn + HC1 = ZnCl 2 + H. 



ZnS0 4 + (NHJ 2 S - ZnS + (NH 4 ) 2 SQ 4 
ZnCl 2 + KOH = Zn(OH) 2 + KC1. 

Query. Are all of the metals of the third group precipitated with 
ammonium sulphide ? 

Sug. Separate and identify Ni and Co thus : To a solution of their salts 
add KCy until the precipitate at first formed dissolves ; slightly acidulate 
with HC1, and boil some time ; a little HC1 now precipitates NiCy 2 . 



THE RARE METALS OF GROUP III. 
BERYLLIUM. 

Symbol, Be. — Atomic Weight, 9. 

322. Beryllium, also known as Glucinum, is a silver -white 
metal occurring in Beryl, Be 3 Al 2 Si 6 18 . 

It is prepared by fusing BeCl 2 with metallic sodium or 
potassium. 

The salts of beryllium haye a sweetish taste, from which 
fact the metal first received the name glucinum. 



INDIUM. — GALLIUM. 303 

In the regular course of analysis beryllium is obtained along 
with aluminum, from which metal it can be separated by pre- 
cipitation with (NH 4 ) 2 C0 3 . 

INDIUM. 

Symbol, In. — Atomic Weight, 114. 

323. Indium occurs in zinc blende, and was discovered by 
means of the spectroscope. It is a soft, white metal which 
scarcely undergoes any change in the air. It is prepared from 
its ores in the wet way. 

Indium is detected by moistening its compounds with hydro- 
chloric acid ; then it is placed in the non-luminous Bunsen flame 
by means of a looped platinum wire. It colors the flame blue. 

GALLIUM. 
Symbol, Ga. — Atomic Weight, 70. 

324. This metal also occurs in zinc blende, and was dis- 
covered by the spectroscope. Its more prominent properties 
were predicted previous to its discovery by Mendelejeff, under 
the name of " Ekaluminum." (See p. 222.) It is prepared in 
the wet way, and is a bluish-white metal, oxidizing readily in 
the air, and melting at the extremely low temperature of 30.1° C. 

It is detected by the spectroscope. Its luminous spectrum 
contains two violet lines. 

Note. The luminous spectrum is obtained by igniting a substance on 
platinum wire in the Bunsen flame, or by means of a powerful cur- 
rent of electricity, and exposing the flame directly to the spectroscope. 
The absorption spectrum is obtained by igniting as above, and placing a 
luminous gas-flame or other absorbing material between the burning metal 
and the spectroscope. The spark spectrum is obtained by moistening the 
carbon terminals of a dynamo or other powerful electric machine with a 
solution of the substance to be tested, after which sparks are allowed to 
pass. 



30-4 YTTRIUM. LANTHANUM. CERIUM. DIDYMIUM. 

YTTRIUM. 

Symbol, Yt. — Atomic Weight, 89 . 

325. Yttrium occurs along with erbium. 

It is detected b} 7 the spark spectrum of its chloride, which 
gives man} 7 bright lines, of which the most marked are two 
groups near the sodium line. 

LANTHANUM. 

Symbol, La. — Atomic Weight, 138.9. 

326. Lanthanum occurs in the mineral Lanthanite as La 2 (C0 3 ) 3 
+ 8 H 2 0. It is best prepared by the electrolysis of its chloride, 
and is a soft grayish metal which readily tarnishes in the air, 
assuming a steel-blue tint. It is detected by its spark spectrum 
containing many characteristic lines. 

CERIUM. 

Symbol, Ce. — Atomic Weight, 140. 

327. Cerium occurs along with Lanthanum, and is similarly 
prepared. It is a soft, gray metal which tarnishes in damp air, 
assuming, successively, the colors yellow, blue, and green. 

It burns with great brilliancy when heated in the air, and 
is detected by its spark spectrum which contains three bright 
lines in the green. 

DIDYMIUM. 

Neodymium, Nd, 143.5. — Praesodymium, Pr, 140.5. 

323. This metal occurs along with the rare metals previously 
mentioned, and is prepared similarly to Lanthanum. It has a 
yellowish lustre, and burns brightly when heated in the air. 

It is detected b} 7 its absorption spectrum. Its salts have a 
rosy tint, and it colors the microcosmic bead rose-red. 



TEKBIUM. — EKBIUM. — THORIUM. TITANIUM. 305 

TERBIUM. 

Symbol, Tb. — Atomic Weight, 160. 

329. This metal has not been prepared, but its oxide, Tb 2 3 , 
is an orange-yellowish powder. It is difficult to separate ter- 
bium from the preceding kindred metals, and no sure means of 
detection is known, since it gives no absorption spectrum. 

ERBIUM. 

Syivibol, Er. — Atomic Weight, 166. 

330. This metal occurs with the foregoing, and has not been 
obtained pure. It is detected by its continuous luminous spec- 
trum, which is crossed by bright lines which are darkened in 
the same position in the absorption spectrum. 

THORIUM. 

Symbol, Th. — Atomic Weight, 232.5. 

331. Thorium occurs in Thorite and other complex minerals, 
and is prepared by heating its chloride with potassium. This 
metal as thus prepared is a gray powder which burns brightly 
in the air. Thorium salts are radio-active. 

Thorium is detected by the precipitation of its carbonate or 
hydroxide ; these are soluble in an excess of the precipitant. 

TITANIUM. 
Symbol, Ti. — Atomic Weight, 48. 

332. This metal occurs in Eutile and in Titanite, TiCaSi0 5 , 
and other minerals. It forms a considerable per cent of some 
of the Lake Superior iron ores. Titanium is prepared b} T heating 
a double fluoride of potassium and titanium in a closed crucible 
with metallic potassium; the fused mass is then lixiviated with 
water, when the titanium remains as a dark-gray powder. 



306 ZIRCONIUM. — URANIUM. 

At a high temperature this metal unites directly with nitro- 
gen, — a marked peculiarity ; it also burns when heated in 
the air. In blast furnaces, when reducing iron ore containing 
titanium, a peculiar compound, Titanium Cyano-nitride, TiCy 2 
+ 3 Ti 3 N 2 , is obtained. 

Titanium is detected hx imparting to the microcosmic bead in 
the reducing-flame a yellow color when hot, violet when cold ; 
when iron is present the bead is red. The oxidizing-flame 
gives no color. 

ZIRCONIUM. 

Symbol, Zr. — Atomic Weight, 90.6. 

333. Zirconium occurs in the mineral Zircon, ZrSi0 4 , and is 
prepared in the same wa}- as titanium, which metal it strongly 
resembles. The amorphous form burns easily, but a crystalline 
variety takes fire in the air only at the highest temperatures. 

Zirconium is detected by precipitating its sulphate by K 2 S0 4 , 
which gives a basic salt insoluble in water and lrydrochloric 
acid. Its spectrum is characteristic. 

URANIUM. 

Symbol, U. — Atomic Weight, 238.5. 

334. Uranium occurs in pitch blende. U 3 8 , and is prepared 
in the wet way, or by fusing its chloride with potassium. 

This is a hard, grayish-white metal, which also burns in the 
air. 

The black oxide, U 2 5 , is used for painting on porcelain c 
The uranium salts are fluorescent, and impart this property to 
;i canary" glass. 

Uranium is detected by its giving to the microcosmic bead 
in the oxidizing-flame a }^ellow color when hot, green when 
cold ; when farther heated the color is darkened. 

The spectrum of uranium is distinctive. 



TANTALUM. — NIOBIUM. — VANADIUM. 307 

TANTALUM. 

Symbol, Ta. — Atomic Weight, 183. 

335. Tantalum occurs together with many of the rare metals 
previously noticed, but more especially with niobium, from 
which metal it has not been separated. 

Tantalite, Columbite, Pyrochlor, Yttrotantalite, Pitch Blende, 
and many other minerals contain small quantities of this metal. 
Tantalum has not been obtained pure. 

It is detected by converting the compound into tantalic acid, 
and addiug potassium f errocyanide to its solution ; this yields a 
yellow precipitate. The conversion is effected by heating the 
compound with carbon in a current of chlorine to obtain the 
chloride TaCl 5 ; this chloride, when mixed with water, yields 
the acid HTaO s . A solution of nut-galls gives a yellow precipi- 
tate with solutions of this acid. 

NIOBIUM. 

Symbol, Nb. — Atomic Weight, 94. 

336. Niobium occurs with Tantalum, and is prepared by 
passing the vapor of its chloride and hydrogen through a red- 
hot porcelain tube. It is a steel-gray metal, burning easily in 
the air. Niobium is frequently called Columbium. 

Niobium is detected similarly to tantalum, the precipitate with 
K 4 FeCy 6 being brown ; with nut-galls solution, orange-red. 

VANADIUM. 

Symbol, V. — Atomic Weight, 51.2. 

337. This metal occurs in Vanaclanite, 3 Pb 3 (V0 4 ) 2 + PbCl 2 , 
and is prepared as a grayish powder by heating its chloride in 
hydrogen. 



308 VANADIUM. 

Vanadium bronze, or rnetavanadic acid, is now used in place 
of gold bronze for gilding. 

Vanadium is detected by placing a strip of zinc in a solution 
of vanadium chloride ; the solution turns blue. When hydrogen 
dioxide and ether are added to the solution of a vanadate, the 
solution turns red. 

General Note. Observe those formulae like Co(Ni, Fe)As 2 ; these 
do not signify that both M and Fe are present, but that one or the other 
is found in such a compound. 

RADIUM. 

Symbol, Ea. — Atomic Weight, 225. 

Mine, and M. Curie, while working with radio-active sub- 
stances, discovered a new and remarkable element, Eadium. 
It was found in pitch blende, an impure ore of uranium. In 
many respects radium is the most remarkable element yet dis- 
covered. Its compounds maintain a temperature slightly above 
that of the surrounding media. They emit light and other 
radiations which readily penetrate opaque substances. Some 
of these radiations when allowed to penetrate the flesh destroy 
the tissues. These radiations are now undergoing trial as a 
remedy for cancer and other bacterial diseases. 

It has been shown that radium compounds emit three kinds 
of rays : 1st, the a rays are short and easily stopped by opaque 
screens, and are deflected by a magnet ; 2d, the ft rays are also 
deflected by a magnet, and are more penetrating; 3d, the y rays 
are not deflected, and are the most penetrating of all. Eadium 
also induces radio-activity in associated substances. 

Many scientists are now studying the properties of radium, 
and it is believed by some that it is actually undergoing atomic 
dissolution, throwing off small particles which recombine to 
form helium atoms. If these observations prove correct, the 
generally accepted views of the constitution of matter will 
undergo profound modifications. 

Eadium is closely allied to barium in its properties, and 
therefore belongs to the next group. See page 221. 



CHAPTER XVIII. 

THE FOURTH GROUP METALS. 

338. The fourth group metals are commonly known 
as the Metals of the Alkaline Earths. 

Their chlorides, hydroxides, and sulphides are soluble in 
water, acids, and alkalies. In the course of analysis they 
are precipitated as carbonates by ammonium carbonate, 
(NH 4 ) 2 C0 3 , in the presence of ammonia and ammonium 
chloride. We must except magnesium, however, from 
the above statement, since its carbonate is soluble in 
ammonium compounds. It is best to filter out the precipi- 
tates obtained by ammonium carbonate, and to precipitate 
the magnesium from the filtrate by means of di-sodium 
phosphate, Na 2 HP0 4 . 



THE FOURTH GROUP METALS ARE: — 

r Barium, Ba. 
Division A < Strontium, Sr. Division B £ Magnesium, Mg. 

( Calcium, Ca. 
And the rare metal Radium, Ra. 

These metals oxidize easily in the air, and consequently 
never occur free ; they are strongly basic, hence they are 
not easily reduced to a metallic state ; they form no acids ; 
they decompose water to form alkaline hydroxides. 



310 BARIUM. 



BARIUM. 

Symbol, Ba". — Atomic Weight, 137.4. — Specific Heat, — 
Melting -Point, higher than Cast Iron. 

339. Occurrence. — The most abundant ore of this 
metal is Heavy Spar, BaS0 4 . Barium also occurs in small 
quantities in Witherite, or BaC0 3 , in certain silicates in 
feldspathic rocks, in seaweeds, and in mineral waters. 

340. Preparation. — Barium amalgam is prepared by 
electrolyzing a thick paste of BaCl 2 and dilute HO in the 
presence of mercury. This amalgam is then heated to 
vaporize the mercury, thus leaving a porous mass of 
metallic barium. Barium oxidizes rapidly in the air, and 
burns with great brilliancy. 

341. Compounds and Uses of Barium. — Metallic 
barium is not used in the arts. 

ITS PRINCIPAL COMPOUNDS ARE: — 

(a) Barium Monoxide, or Baryta, BaO, which is prepared by 
heating the nitrate until nitrous fumes cease escaping. 

Barium Hydroxide, or Caustic Baryta, Ba(OH) 2 , is obtained 
by moistening BaO with water ; a solution of this hydroxide 
is used as a reagent known as Baryta Water. Caustic baryta 
was largely used in refining cane sugar, which it precipitates 
from its impure solutions as C 12 H 22 O n BaO. The barium is after- 
wards removed by treatment with carbon dioxide gas, which 
precipitates the insoluble compound, BaC0 3 , while the sugar 
dissolves. 

Barium hydroxide is now prepared in large quantities by 
passing moist carbon dioxide gas through heated barium sul- 



BARIUM. 311 

phide, which gives BaC0 3 ; this carbonate is then treated with 
superheated steam, when this reaction occurs : — 

BaC0 3 + H 2 = Ba(OH) 2 + C0 2 . 

(b) Barium Chloride, BaCl 2 . This salt is used as a reagent 
to detect and estimate sulphuric acid ; it is prepared by dissolv- 
ing barium carbonate, BaC0 3 , in hydrochloric acid. Write the 
equation. 

(c) Barium Iodate, Ba(I0 3 ) 2 , which is used to prepare iodic 
acid, HI0 3 ; this iodate is prepared thus : — 

BaCl 2 + 2 KI0 3 = Ba(I0 3 ) 2 + 2 KCL 

(d) Barium Sulphate, or Heavy Spar, BaS0 4 . This mineral 
is an important barium ore, used for weighting paper and as a 
paint. It is prepared for commerce thus : — 

BaCl 2 + H 2 S0 4 = BaS0 4 + 2 HC1. 

(e) Barium Nitrate, Ba(N0 3 ) 2 . This is prepared thus : — 

BaC0 3 + 2 HN0 3 = Ba(N0 3 ) 2 + H 2 + C0 2 . 

It is used in making green fires for tableaux and pyrotechnics. 

(/) Barium Carbonate, BaC0 3 , which occurs in nature as 
Witherite; it is also the group-reagent precipitate, prepared by 
precipitating a barium salt bjvmeans of an alkaline carbonate. 
It is largely used to prepare soluble barium salts. 

342. Tests for Barium. — 1. Solids are fused with 
sodium carbonate, if necessary, and then dissolved in 
hydrochloric or nitric acid ; this solution gives these pre- 
cipitates : — 

(a) With K 2 Cr 2 7 and ammonia, a yellow precipitate, 
BaCr0 4 , insoluble in acetic acid. 

(5) With H 2 S0 4 , a white precipitate, BaS0 4 , insoluble 
in acids. 

(c) CaS0 4 gives an immediate precipitate of BaS0 4 
even in dilute solutions. 



312 STRONTIUM. 

2. Barium salts tinge the non-luminous flame green. 

3. The barium spectrum, although complicated, is 
readily distinguished by the green lines Baa and Ba/3. 

STRONTIUM. 

.Symbol, Sr". — Atomic Weight, 87.6. — Melting -Point, 

a red heat. 

343. Occurrence. — Strontium occurs most plentifully 
in the two ores, Celestine, SrS0 4 , and Strontianite, 
SrC0 3 . It also occurs in a few mineral waters and in 
sea-water. 

344. Preparation. — This metal is prepared by electro- 
tyzing its chloride, or by heating this compound with a 
sodium amalgam ; the strontium amalgam thus formed is 
then washed, dried, and, finally, ignited in a current of 
hydrogen. 

345. Properties, Compounds, and Uses of Strontium. 

— Strontium is a yellow, malleable metal, oxidizing in the 
air, and burning brightly when heated. 

THE PRINCIPAL STRONTIUM COMPOUNDS ARE : - — 

(a) Strontium Carbonate, SrC0 3 . This precipitate is ob- 
tained by precipitating a strontium salt solution with an alkaline 
carbonate. 

(b) Strontium Nitrate, Sr(N0 3 ) 2 . This is prepared thus : — 

SrC0 8 + 2 HN0 3 = Sr(N0 3 ) 2 +H 2 + C0 2 . 

It is used in producing red fire for tableaux, etc. Material for 
red fire is best produced by mixing about equal parts of finely 
pulverized and thoroughly dried Sr(N0 3 ) 2 and KC10 3 with an 



CALCIUM. 313 

equal bulk of powdered shellac, or with one-fourth part flowers 
of sulphur ; the shellac is preferable, as it gives off no suffo- 
cating fumes of sulphur dioxide. Green fire is obtained simi- 
larly, by using barium nitrate, Ba(X0 3 ) 2 , in place of strontium 
nitrate. 

Caution. These ingredients must be powdered separately, and after 
wards mixed with a bone knife on paper, since any concussion may pro- 
duce an explosion. 

346. Tests for Strontium. — 1. Most strontium com- 
pounds, when moistened with hydrochloric acid, impart a 
beautiful crimson tint to the non-luminous flame. Sul- 
phates should be reduced to sulphides in the reducing- 
flame and then moistened with HC1 before ignition. 

Xote. When both barium and strontium are present, the strontium 
color appears when the substance is first brought into the flame. A cau- 
tion, also, is needed here lest the student mistake the pale yellowish-red 
flame of calcium for that of strontium. Compare the colors yielded by 
the pure salts of these two metals. 

2. The spectrum of strontium contains the prominent 
lines : Sra, orange ; Sr/3, red ; and SrS, blue. 

3. In the wet way, strontium when precipitated with 
carbonates, phosphates, and oxalates, resembles barium. 
It maj T be separated from barium by precipitating the latter 
with ammonia and K 2 Cr 2 07. It may be separated from 
calcium by precipitating strontium with CaS0 4 . 

CALCIUM. 

Symbol, Ca". — Atomic Weight, 40. — Specific Heat, 
0.1804. — Melting -Point, a red heat. 

347. Occurrence. — The most abundant compound of 
calcium is the carbonate, CaC0 3 . This mineral occurs in 
enormous quantities and widely distributed; uncrystal- 



314 CALCIUM. 

lized CaC0 3 occurs as limestone and chalk ; the crystal- 
lized forms are many, such as marble, Iceland Spar, Calc 
Spar, and Dog-tooth Spar. Shells and corals are chiefly 
carbonates of calcium, while bones and teeth are princi- 
pally phosphates of this metal. Calcium Sulphate, CaS0 4 , 
occurs in Gypsum, Anhydrite, and Selenite. Some moun- 
tain ranges and geological formations are chiefly composed 
of these calcium compounds. 

348. Preparation. — This metal is prepared by electro- 
lyzing its chloride, or by fusing calcium iodide with 
metallic sodium in closed iron retorts. 

349. Properties, Compounds, and Uses of Calcium. — 

Calcium is a malleable metal, which oxidizes most rapidly 
in moist air, and burns with an orange-yellow light. 

THE MOST USEFUL COMPOUNDS OF CALCIUM ARE: — 

(a) Quick-lime, CaO, prepared by heating the carbonate, 
CaC0 3 . Give the equation. 

Calcium Hydroxide, Ca(OH) 2 , which is prepared by treating 
CaO with water. "When this substance is in a dry powder or of 
the consistency of paste, it is called "slaked lime." Why? A 
saturated water solution of calcium hydroxide, called lime- 
water, is used as a reagent for detecting free carbon dioxide 
gas. 

Slaked lime is used for many purposes, such as for making 
mortar, purifying illuminating gas, whitewashing, etc. Mortar 
consists of sand, three to four parts, and lime, one part, 
thoroughly mixed with water. 

Sug. Describe the method of making mortar. (Ask a mason or 
plasterer, if you do not know.) What is "putty coat" or "hard finish" ? 

Lime containing about ten per cent of silica is known as 
hydraulic cement or water-lime, and possesses the peculiar 



CALCIUM. 315 

property of hardening under water. This cement is artificially 
prepared by mixing finely pulverized burnt clay and limestone. 
Calcium hydroxide absorbs carbonic acid gas from the air, 
which fact explains the hardening of the mortar. It may also 
combine with the silica. 

Query. Does age improve the hardness of cement or mortar ? Does 
the cement of the ancient Roman masonry owe its stone-like character to 
its age or to the process of manufacture q 

(b) Gypsum, CaS0 4 + 2 H 2 0. This occurs native, and 
when ground is used as land plaster ; when calcined, it is 
known as u Plaster of Paris," which is used in making casts 
and for filling writing-paper. 

Query. What is the object of the calcining 1 Explain the setting of 
the plaster. 

(c) Calcium Chloride, CaCl 2 . This substance is prepared by 
dissolving Iceland spar or pure marble in hydrochloric acid. 
When fused, it is used as a dryer for gases, owing to its great 
absorptive power, for moisture. 

(d) Fluor Spar, CaF 2 , a well-known mineral used in prepar- 
ing fluorine compounds. 

(e) Bleaching Powder. This is an article of commerce, and 
one of the most useful substances known to the arts. It is 
made by passing chlorine gas into large chambers, on the floors 
of which slaked lime is spread. It is used in bleaching paper, 
rags, cotton goods, etc. This powder affords a convenient 
source of chlorine, which is liberated by the addition of an acid, 
as sulphuric or hydrochloric acid. 

Query. Upon what does the bleaching power of chlorine depend ? 

(/) Superphosphate of Lime is a substance obtained by treat- 
ing bones with sulphuric acid ; it is used in preparing phos- 
ymorus, and also as a fertilizer. The superphosphate is a mix- 
ture of calcium sulphate and acid phosphate. 

(g) Calcium Carbonate, CaC0 3 , previously mentioned under 



316 MAGNESIUM. 

the carbonates. This substance forms one of the constituents 
called u hardness" in drinking-water (see p. 49). 

When a soap is brought into a hard water, insoluble calcium 
salts are formed with the organic acids contained in the soap ; 
hence the peculiar, unpleasant feeling experienced on attempt- 
ing to wash the hands with soap in hard water. All the cal- 
cium carbonate in solution must be precipitated before the 
soap will act in the desired way and form a lather. 

Iceland Spar, a beautiful crystalline variety, possesses the 
property of " double refraction." 

350. Tests for Calcium. — 1. The volatile calcium salts 
tinge the flame orange-reel. 

2. The spectrum shows the green line Ca/3 and the 
orange line Caa, which are distinctive. 

3. In solutions, calcium may be separated from barium 
and strontium by precipitating the latter metals with 
K 2 S0 4 ; to the filtrate ammonia and ammonium oxalate, 
(NH 4 ) 2 C 2 4 , are added ; the oxalate gives a white precipi- 
tate, CaC 2 4 , which under the circumstances is distinctive. 

Query. Is calcium sulphate easily soluble in water ? Try it. 

MAGNESIUM. 

Symbol, Mg". — Atomic Weight, 24.3. — Specific Heat, 0.245. 
Melting-Point, 750°. 

351. Occurrence. — Magnesium ores are found plenti- 
fully in many localities, among which we notice : Magne- 
site, MgC0 3 ; Dolomite, CaMg(C0 3 ) 2 : Kieserite, MgS0 4 + 
ILO; Carnallite,(Mg,K)Cl 2 + 6H 2 b; Spinelle, MgOAl,0 8 ; 
Asbestos, (Mg,Ca)Si0 3 ; Talc, Mg 3 H 2 (Si0 3 ) 4 ; and Meer- 
schaum, Mg 2 H 2 (Si0 3 ) 3 . 

Magnesium sulphate also occurs in certain medicinal 
springs, while the chloride is a constituent of sea-water. 



MAGNESIUM. 317 

Magnesium limestone is a double carbonate of calcium 
and magnesium. 

352. Preparation. — Magnesium, like calcium, may be 
prepared by the electrolysis of its chloride, but the com- 
mercial article is obtained by fusing a mixture of the dry 
chloride, fluor spar, and metallic sodium in a closed cruci- 
ble. The metal is afterward purified by distillation, and, 
when in a semi-molten condition, it is pressed into wires, 
which are flattened finally into ribbons. 

353. Properties, Uses, and Compounds of Magnesium. 

— Magnesium is a silver-white metal, quite permanent in 
dry air; in damp air, however, its surface becomes coated 
with oxide. It takes fire readily in any ordinary luminous 
flame, and burns with a painfully bright ' and dazzling 
light, which is very rich in chemical rays. Owing to this 
important property, magnesium ribbon is now employed in 
photographing caverns and other objects inaccessible to 
the sun's rays. This metal is also employed in pyrotechny 
and signaling. It is further employed in chemical analy- 
sis, especially in cases of arsenic poisoning, in place of 
zinc, since magnesium contains no traces of arsenic. 

THE MOST IMPORTANT COMPOUNDS OF MAGNESIUM ARE 
THE FOLLOWING : — 

(a) Magnesia, MgO, which is prepared by igniting the car- 
bonate, MgC0 3 . It is used in medicine. 

(b) Magnesium Chloride, MgCl 2 , is obtained from sea-water 
and salt springs. It is used in dressing cotton goods. 

(c) Epsom Salts, MgS0 4 + 7 H 2 0, are prepared from Kie- 
serite, or by treating MgC0 3 with sulphuric acid. It is used in 
medicine as a cathartic, and is also used in dressing cotton 
goods. 



318 REACTIONS IN GROUP IV. 

(d) Magnesium Carbonate, or Magnesite, MgC0 3 , an ore of 
magnesium. This is artificially prepared by roasting dolomite, 
and treating the moistened residue with carbon dioxide gas under 
pressure ; a bicarbonate is thus formed, which is decomposed by 
means of superheated steam. This compound as thus formed 
is a white powder, which is an important article of commerce. 
It is used in medicine ; also used as a face-powder. 

354. Tests for Magnesium. — 1. After removing the 
metals of the fourth group by ammonium carbonate, etc., 
di-sodium phosphate, Na 2 HP0 4 , when added to the filtrate, 
throws down a white precipitate, MgNI^POi; this forms 
in a dilute solution after stirring the solution with a glass 
rod for a few minutes. This precipitate, under the circum- 
stances, is distinctive. 

Note. The spectrum of magnesium is not a practical test, as it is not 
very marked at the temperature of the Bunsen flame. 

355. Separation and Identification of the Fourth 
Group Metals. — 1. Make the solution to be tested neu- 
tral or slightly alkaline, and then remove the metals of 
Groups I., II., and III. by the usual methods. 

Save the filtrate, and boil for some time to expel free 
H 2 S; filter. 

2. Add ammonia, NH 4 C1, and (NH 4 ) 2 C0 3 to precipitate 
barium, strontium, and calcium. Filter out this precipi- 
tate, and save it to test by 3 ; also save the filtrate, and 
test it by 4 for magnesium. 

3. Dissolve this precipitate in acetic acid. 

(a) Test a small portion of the solution for barium 
!>y adding K 2 Cr 2 7 and ammonia; a yellow precipitate, 
BaCr0 4 , indicates barium. If barium be present, thus re- 
move it from the whole solution. This precipitate may 
be filtered out and dissolved in hydrochloric acid ; then, 



BEACTTONR TTC GROUP TV. 319 

upon addition of H 2 S0 4 , the insoluble sulphate, BaS0 4 , 
will confirm the test. 

(&) Test a portion of the filtrate from (a) for calcium 
by Art. 350, 3. 

(c) Precipitate the calcium and strontium from the fil- 
trate not used in (b) by means of ammonia and ammonium 
carbonate. Filter out the precipitate, and dissolve it in 
HC1, and expel excess of acid; then add CaS0 4 . A white 
precipitate, SrS0 4 , formed after a few minutes, indicates 
strontium. Further test this precipitate by 346, 1. 

4. To the filtrate from 2 add Na 2 HP0 4 , and stir for 
some time with a clean glass rod, if necessary; a white 
precipitate, MgNH 4 P0 4 , indicates magnesium. 

REACTIONS IN GROUP IV. 

(1) CaCl 2 + (NH 4 ) 2 C0 3 = CaC0 3 + NH 4 C1. 

(2) Sr(N0 3 ) 2 + (NHJ 2 C0 3 = SrCO a + NH 4 NO s . 

(3) BaCl 2 + (NHJ 2 CO s =? BaCQ 3 + NH 4 C1. 

(4) MgS0 4 + Na 2 HP0 4 = MgHP0 4 + Na 2 S0 4 . 

(5) CaC0 3 + H(C 2 H 3 2 ) = Ga(C 2 H 3 2 ) 2 + H 2 + C0 2 

(6) SrC0 3 + H(C 2 H 3 2 ) = Sr(C 2 H 3 2 ) 2 + 

(7) BaC0 3 +H(C 2 H 3 2 ) = 

(8) Ca(C 2 H 3 2 ) 2 + (NH 4 ) 2 CA= CaCA+ (NH 4 )(C 2 H 3 2 ). 

(9) Ba(C 2 H 3 2 ) 2 + K 2 Cr 2 7 + H 2 + NH 3 = BaCrQ 4 + KC 2 H 3 2 

+ (NH 4 ) 2 O0 4 . 

(10) Ba(C 2 H 3 2 ) 2 + H 2 S0 4 = BaSQ 4 + H(C 2 H 3 2 ). 

(11) BaCl 2 + K 2 C0 3 = BaC0 3 +KCl. 

(12) MgS0 4 +Na 2 C0 3 = MgCO s + 

(13) CaC0 3 +HCl = + 

Sue The student should do much work with the preceding groups; 
the quickest way to become acquainted with a substance is to work with 
it. Unknown solutions give an added zest to the student's desire for 
mastering processes. 



CHAPTER XIX. 



THE FIFTH GROUP METALS. 



356. The metals of the fifth group are known as the 
u Metals of the Alkalies." They do not yield precipitates 
with the usual reagents, since the compounds thus formed 
are soluble; but they are detected by the color which 
their compounds impart to the non-luminous flames, or by 
their spectra. 

These metals are Potassium and Sodium, also the com- 
pound Ammonium, NH 4 ; the rare metals are Lithium, 
Rubidium, and Caesium. 

Of course ammonium is not to be considered a true 
metal, but its compounds are alkaline, and it behaves 
much like metals of this group. In distinction from the 
other or " Fixed Alkalies," ammonium is termed the "Vol- 
atile Alkali," since most of its salts are volatile. 

The metals of this group form a natural series ; they 
are all acted upon by the moisture of the air, and hence 
they must be kept under naphtha ; all decompose water at 
ordinary temperatures to form strongly alkaline hydrox- 
ides ; each one forms but one series of salts, many of 
which are exceedingly stable and useful. 

Queries. To what group do these metals belong in MendelejefPs 

Table % Which belong to the \ series ? Does Na or K show the 

( even 

more intense action when thrown upon the water ? 



POTASSIUM. 321 



POTASSIUM. 



Symbol. K. — Atomic Weight, 39. — Specific Heat, 
0. 1655 ( ? ) . — Meltixg-Poixt, 62.5°. 

357. Occurrence. — The potassium-bearing compounds 
are widely distributed; they occur in mineral waters, sea- 
waters, and all fruitful soils, and are utilized by plants and 
animals. Sheep excrete, through the skin, potassium and 
other compounds, termed " Fat " and Suint. These com- 
pounds are of considerable commercial value; they are 
retained by the wool, of which, before washing, they con 
stitute nearly one-third part by weight. 

Some potassium compounds are the following minerals : 
Sylvite, KC1; Saltpetre, KNO s ; Orthoelase. K 2 AL(Si 3 8 ) 2 ; 
Carnallite, (KMg)Cl 3 ; and Alum. K 2 A1 2 (S0 4 ) 4 + 24 H 2 0. 

358. Preparation. — Acid potassium tartrate is first 

heated in closed iron retorts ; in this way. a very intimate 
mixture of potassium carbonate and carbon is obtained. 
This mixture is then placed in iron tubes covered with 
clay, which are afterwards placed in a furnace, and heated 
to a white heat. Metallic potassium is given off in the 
form of vapors, which are passed into shallow, box-like 
condensers placed outside the furnace ; in these con- 
densers they are quickly cooled to a liquid state : the 
liquid potassium then flows out into vessels containing 
rock oil. (See Fig. 20.) 

Formerly frequent explosions occurred, owing to the 
formation of a black substance, KCO ; but this trouble 
is now obviated by the shallow condensers. 

Sir Humphry Davy first prepared potassium by electro- 
lyzing the moistened hydroxide. This marked a new era 



322 POTASSIUM. 

in chemistry, as the alkalies were previously supposed to 
be elements; and, moreover, with the discovery of potas- 
sium, the discovery of other rare metals became possible. 

Query. What rare metals are now prepared by the aid of metallic 
potassium or sodium ? 

359. Properties, Uses, and Compounds of Potassiunic 

— Potassium is a silver-white metal when first cut, but 
soon afterward exposes a bluish surface. It is brittle at 
0° C, and waxy at ordinary temperatures. 

It ignites at a low heat, — often while being cut, — 
and requires the utmost care while being handled; it 
must be kept under rock oil or naphtha. It quickly 
decomposes water, liberating hydrogen with such violence 
that it frequently takes fire and explodes. 

It dissolves in ammonia, forming a blue solution, from 
. which it may be again obtained unchanged. The princi- 
pal use of metallic potassium, other than for class demon- 
stration, is in preparing the rare metals, as previously 
noticed. 

THE PRINCIPAL POTASSIUM COMPOUNDS NOT HERETO- 
FORE NOTICED ARE: — 

(a) Potassium Hydroxide, or Caustic Potash, KOH. This is 
prepared by treating potassium carbonate with slaked lime, 
thus : — 

K 2 C0 3 +Ca(OH) 2 = 2 KOH + CaC0 3 . 

The aqueous solution thus prepared is evaporated to dryness, 
fused, and marketed. In this condition, it is extensively used 
as a lye. It is purified for reagent purposes by dissolving the 
crude salt in alcohol, and, after evaporation, again fusing and 
casting it into sticks. It is kept in air-tight bottles, since it has 
a powerful attraction for carbon dioxide and moisture, and soon 



POTASSIUM. 323 

deliquesces ; neither must it be handled with the hands, since it 
destroys the skin. 

Sug. Leech some common wood ashes by passing water through them 
Examine the filtrate obtained. 

(b) Potassium Chloride, KC1, occurs naturally as Sylvite, 
and in many brines. It is used as a fertilizer and in preparing 
other potassium salts. 

(c) Potassium Bromide, KBr. This salt is obtained together 
with bromate of potassium by dissolving bromine in potassium 
hydroxide ; the bromate is afterwards decomposed by a gentle 
heat. It is used in medicine as a sedative, and in the labora- 
tory as a source of bromine for demonstration. 

Query. How is Br prepared 2 

(d) Potassium Iodide, KI, may be prepared in the same way 
as the bromide. It is used extensively in medicine and for 
other purposes ; in the laboratory it is a source of iodine for 
purposes of demonstration and is a reagent. 

Sug. The potassium salts will be found in the laboratory; let the 
student examine them, note the forms of the crystals, etc., and write a 
description. 

(e) Potassium Chlorate, KC10 3 , is obtained by passing a cur- 
rent of chlorine gas through a solution of caustic lime until 
calcium chlorate, Ca(C10 3 ) 2 , is formed; potassium chloride is 
then added with the following results : — 

Ca(C10 3 ) 2 + 2 KC1 = 2 KCIO3 + CaCl 2 . 

The chlorate of potassium is obtained from this solution by 
crystallization. This salt is used in medicine for inflammation 
of the throat, and in the laboratory as a source of oxygen. 

Query. How is oxygen obtained from KC10 3 ? How may potassium 
chlorate be prepared from chlorine and potassium hydroxide ? How is 
KC10 4 prepared ? (See Perchloric Acid. ) 

(/) Potassium Sulphate* K 2 S0 4 , occurs native, and is pre- 
pared as a by-product in the manufacture of other potassium 



324 POTASSIUM. 

compounds, as the bichromate, etc. It is used in medicine as 
a purgative ; it is further used in the manufacture of alum, and 
in the laboratory as a reagent. 

An acid sulphate, KHS0 4 , is obtained in manufacturing 
nitric acid. 

Sug. Write the equation. 

(g) Saltjietre, or Nitre, KN0 3 , occurs as an incrustation on 
the soil of some hot, dry climates, as in India and in Egypt, where 
it is produced by the oxidation of nitrogenous organic substances 
in contact with the potassium compounds contained in the soil. 
It has recently been shown that the formation of nitrates which 
takes place in the soil is caused by minute organisms or fer- 
ments. The process is similar to the familiar fermentation of 
sugar, which causes the formation of alcohol and carbon 
dioxide. 

It is artificially prepared by treating sodium nitrate, which 
occurs native in immense deposits, with potassium chloride, 
thus : — 

NaN0 3 + KC1 = KN0 3 + NaCl ; 

and also in the so-called " saltpetre plantations." These are 
constructed by piling up refuse animal matter, mixed with wood 
ashes and lime, and moistening with urine or stable drainings. 
At intervals the outer layer is removed, and extracted with 
water. 

The term " saltpetre" is derived from the fact that this salt 
was and is still obtained from certain oily or feldspathic rocks 
by boiling the weathered rock with slaked lime and potash. 

Saltpetre is used in the laboratory as a source of nitric acid 
for demonstration, as an oxidizing agent (substances are fused 
with KNO3 for this purpose), and in preparing cooling mix- 
tures. 

Query. How are freezing mixtures prepared ? Explain the philoso- 
phy of the process. 



POTASSIUM. 325 

In domestic economy, it is used as a preservative of meat ; 
but the most important purpose for which nitre is used is in 
manufacturing gunpowder. 

Gunpowder consists of an intimate mixture of nitre, sulphur, 
and charcoal, in somewhat varying proportions. Sporting pow- 
der consists of nitre, 78.99, sulphur, 9.84, and charcoal, 11.17 
parts. The explosive force of gunpowder depends upon the 
fact that it contains within itself the necessary amount of oxy- 
gen for its own combustion, whereby large volumes of heated 
gases (principally carbon dioxide and nitrogen) are liberated. 

Query. What effect has the invention of gunpowder had on civiliza- 
tion ? Give the philosophy of explosions in general. 

(li) Potassium Carbonate, or Potash, K 2 C0 3 , is usually ob* 
tained from wood ashes. The ashes are lixiviated or " leached, " 
and the lye thus obtained is evaporated till the solution is satu- 
rated, when impure crystals of the carbonate are deposited. 
These crystals are purified by roasting in a reverberatory 
furnace. 

Other sources of potash are potassium sulphate, beet-root 
ashes, and suint. 

Potassium carbonate is used in preparing other salts, as 
potassium cyanide, chromate, acetate, etc., and as a reagent. 

An acid salt, KHC0 3 , is prepared by passing a current of 
carbon dioxide gas through a solution of the normal carbonate. 

(i) Potassium Cyanide, KCN or KC} T , is an important com- 
pound, used in the laboratory as a reducing agent ; also used in 
photography, and as a solvent for silver sulphide or oxide. 

It is prepared by heating the ferro-cyanide with the carbo= 
a ate to a red heat in iron crucibles, thus : — 

K 4 Fe(CN) 6 + K 2 C0 3 == 5 KCN + KCNO + C0 2 + Fe. 

The chemically pure cyanide is prepared by passing hydrocyanic 
acid gas into an alcoholic solution of potassium hydroxide. 
(j) There are other potassium salts in which the metal is 



326 sodium. 

combined with organic acids, and some of which are used in the 
laboratory. 

The student will notice the tartrate, oxalate, and acetate. 

360. Tests for Potassium. — 1. Potassium compounds, 
on the platinum loop, color the Bunsen flame violet; but 
the presence of sodium obscures this test, hence it is neces- 
sary to observe the flame through thick cobalt-blue glass, 
which shuts off the sodium rays but transmits the potas 
sium color. 

Note. Always thoroughly clean the wire before testing. 

2. The spectrum furnishes two easily distinguished 
lines, — Ka in the extreme red, and K/3 in the violet. 

3. Potassium salts, in concentrated solutions, and in the 
absence of all non-alkaline bases, yield, with tartaric acid, 
a white, distinctive precipitate, KHC 4 H 4 6 , this is granular- 
crystalline,, and may be tested further by 1. 

SODIUM. 

Symbol, Na ; . — Atomic Weight, 23. — Specific Heat, 0.2394. 
— Melting-Point, 95.6°. 

361. Occurrence. — The chief and most plentiful sodium 
compound is common salt, sodium chloride, NaCl. Salt 
occurs in sea-water, most mineral waters, and drinking 
water, while traces of it are to be found in nearly all river 
waters. In some localities in the United States — as at 
Syracuse, N.Y., and the Saginaw Valley, Mich. — salt 
water or brine is found in vast reservoirs at a considerable 
depth below the surface of the earth. Wells are sunk in 
such localities, and the brine is raised to the surface by 
pumps, and utilized as a source of the salt used in com- 
merce. Again, large beds of native salt or rock salt occur 
in various localities. 



SODIUM. 



327 



Another source of sodium is the native nitrate, XaN0 3 , 
or Chili saltpetre, which occurs in beds in Chili and Peru. 

A large tract of territory in the western United States 
is known as the Alkali Plains, owing to the occurrence of 
sodium compounds: the water and the very earth itself 
are saturated with alkali to such an extent that but scant 
vegetation grows, and, with the exception of one or two 
species of worms, the waters of the lakes, although clear 
as crystal, are uninhabited. 




Fig. 20. 

A is the iron tube retort coated with clay. 

C is the condenser. 

D is the cup containing rock oil. 

In its distribution, sodium is the most persistent and 
universal of all the metals ; indeed, it is nearly impossible 
to find a compound that will not yield the sodium test. 



362. Preparation. — Sodium is prepared precisely like 
potassium, excepting that the carbonate and charcoal, 
instead of the tartrate, are employed. It is somewhat 



328 SODIUM. 

more easily obtained, however, and no explosive compound 
is formed. 

Fig. 20 will give a good idea of the furnace employed 
in obtaining metallic sodium and potassium. After the 
condenser is filled with the metal, it is taken off and put 
under rock oil, after which the metal is scratched off. 

363. Properties, Uses, and Compounds of Sodium. — 

Sodium is a light, silver- white metal which oxidizes readily 
in damp air. 

It does not act upon water with as much violence as 
potassium, but it will take fire when thrown upon hot 
water, starch paste, or wet paper. 

Queries. What purpose does the starch paste serve ? Explain the 
phenomenon of sodium burning on hot water. What metals are obtained 
by the aid of metallic sodium ? 

SODIUM FORMS MANY USEFUL SALTS, OF WHICH WE 
NOTICE THE FOLLOWING : — 

(a) Sodium Hydroxide, or Caustic Soda, NaOH, is prepared 
on the large scale by decomposing sodium carbonate with 
slaked lime, thus : — 

Ca(OH) 2 + Na 2 C0 3 = 2" NaOH + CaC0 3 . 

The aqueous solution is then treated precisely in the same man- 
ner as caustic potash. Caustic soda is also prepared in large 
quantities from the red liquors from which the black crystals 
obtained in the soda-ash process are deposited. 

Queries. When metallic sodium acts on water, is NaOH obtained ? 
Try it. How can you decide what this substance is ? 

The principal use of caustic soda is in soap making. In the 
laboratory it is a useful reagent. 

(b) Sodium Chloride, or Common Salt, NaCl, is obtained 
from various sources, as previously indicated. The strong 
brine of the salt wells is evaporated in shallow tanks by the aid 



SODIUM. 



329 



of steam until the salt crystals are deposited. Salt is obtained 
from sea-water by allowing it to flow into large, shallow pans or 
vats called " salterns," where it is evaporated through the agency 
of the wind and sun. 

Sug. Student mention the many uses of common salt. 

(c) Sodium Nitrate or Chili Saltpetre, NaN0 8 , occurs in vast 
deposits in Peru and Bolivia, and is now used as a source of 
nitric acid and as a fertilizer. 

Queries. What other use of NaN0 3 was mentioned above under 
potassium ? What element is obtained from Chili saltpetre 1 

(d) Acid Sodium Hyposulphite, NaHS0 2 , is obtained by 
treating a solution of sodium hydrogen sulphite, NaHS0 3 , with 
granulated zinc. 

It is used by dyers and calico printers to reduce indigo, and 
in the laboratory for estimating free oxygen quantitatively. 

(e) Sodium Sulphate, Na 2 S0 4 , with some admixture of the 
acid sulphate, NaHS0 4 , is prepared in the first stage in the 
manufacture of soda or sodium carbonate. It is known as 
" salt-cake." 

(/) Sodium Thiosidphate, Na 2 S 2 3 + 5 H 2 0, is used as an 
antichlor by paper manufacturers, and in the photographic proc- 
ess for dissolving out the unaltered silver salts. It is prepared 
by boiling caustic soda with sulphur, and then passing sulphur 
dioxide gas until the yellow solution obtained is decolorized. 
Its solvent action on silver salts is due to the formation of a 
double salt of sodium and silver, NaAgS 2 3 : — 

Na 2 S 2 3 + AgCl = NaAgSA + NaCl. 

(g) Sodium Hypophosphite , NaH 2 P0 2 , is prepared by adding 
calcium hypophosphite to a solution of sodium carbonate. The 
filtered solution is then evaporated in vacuo. It is used in 
medicine. 

(li) Disodium Phosphate, Na 2 HP0 4 , is used in medicine as a 
mild cathartic, and in the laboratory as a reagent. It is pre- 
pared by treating phosphoric acid with sodium carbonate. 



330 



SODIUM. 



(i) Sodium Carbonate, Na 2 C0 3 , is the chief product of soda- 
ash manufacture. Soda-ash is a mixture of the carbonate and 
hydroxide. The normal carbonate is used as an indispensable 
reagent in dry reactions in the laboratory. 

The manufacture of soda-ash is a great industry by itself. 
The English process is thus described by Roscoe : — 

"This substance, known in commerce as soda-ash, is manu- 
factured in England on an enormous scale, and used for glass 
making, soap making, bleaching, and various other purposes in 
the arts. Formerly it was prepared from barilla or the ashes of 
sea-plants, but now it is wholly obtained from sea-salt by a 
series of chemical decompositions and processes, which may be 
divided into two stages : — 

64 1. Manufacture of sodium sulphate, or salt-cake, from 
sodium chloride (common salt) ; called salt-cake process. 

44 2. Manufacture of sodium carbonate, or soda-ash, from 
salt-cake ; called soda-ash process . 




44 1. Salt -Cake Process. — This process consists in the 
decomposition of salt by means of sulphuric acid. This is 
effected in a furnace called the Salt-Cake Furnace. Fig. 21 
shows the section of such a furnace. This is drawn to a scale 
from one actually in use. It consists of (1) a large covered 
iron pan, a, placed in the centre of the furnace, and heated by 
fire placed underneath ; and (2) two roasters or reverberator}' 
furnaces, dd, placed one at each end, and on the hearths of 
which the salt is completely decomposed. The charge of half a 
ton of salt is first placed in the iron pan, and then the requisite 



SODIUM. 331 

quantity of sulphuric .acid allowed to run in upon it. Hydro- 
chloric acid gas is evolved, and escapes through a flue, c, with 
the products of combustion into towers or scrubbers filled with 
coke or bricks moistened with a stream of water. The whole 
of the acid vapors are thus condensed, and the smoke and 
heated air pass up the chimney. By recent act of Parliament, 
the alkali makers are compelled to condense at least 95 per 
3ent of the lrydrochloric acid gas they produce ; and so perfectly 
is this condensation as a rule carried out, that the escaping 
gases do not cause a turbidity in a solution of silver nitrate. 
proving the absence of even a trace of the acid gas. After the 
mixture of salt and acid has been heated for some time in 
the iron pan, and has become solid, it is raked on to the hearths 
of the furnaces at each side of the decomposing pan, where the 
flame and heated air of the fire complete the decomposition into 
sodium sulphate and hydrochloric acid. 



t% 2. Soda- Ash Process. — This process consists (1) in the 
preparation of sodium carbonate, and (2) in the separation and 
purification of the same. The first chemical change which the 
salt-cake undergoes in its passage to soda-ash is its reduction 
to sulphide, by heating it with powdered coal or slack : — 

Na 2 S0 4 + C 4 = N%S + 4 CO. 

The second decomposition is the conversion of the sodium 
sulphide into sodium carbonate, by heating it with chalk or 
limestone (calcium carbonate) : — 

Na 2 S + CaC0 3 = Na 2 C0 3 + CaS. 

These two reactions are in practice carried on at once, a mixture 



332 sodium. 

of ten parts of salt-cake, ten parts of limestone, and seven and 
a half parts of coal being heated in a reverberatory furnace 
called the Balling Furnace (shown in section in Fig. 22) until 
it fuses and the above decomposition is complete, when it is 
raked out into iron wheelbarrows to cool. This process is gen- 
erally termed the black-ash process, from the color of the fused 
mass. 

4 c The next operation consists in the separation of the sodium 
carbonate from the insoluble calcium sulphide and other impuri- 
ties. This is easily accomplished by lixiviation, or dissolving 
the former salt out in water. On evaporating down the solu- 
tion, for which the waste heat of the black-ash furnace is used, 
the heated air passes over an iron pan (see 6, Fig. 22) contain- 
ing the liquid. On calcining the residue, the soda-ash of com- 
merce is obtained." 

Ammonia Process. — Another process for converting sodium 
chloride into sodium carbonate is now used extensively. It 
consists in treating a solution of sodium chloride with ammonia 
and carbon dioxide : — 

NaCl + NH 3 + H 2 + C0 2 = NaCl + NH 4 HC0 3 . 

The acid ammonium carbonate acts upon the sodium chloride, 
forming acid sodium carbonate, NaHC0 3 , which is difficultly 
soluble and is deposited : — 

NaCl + NH 4 HC0 3 = NH 4 C1 + NaHC0 3 . 

The acid carbonate is heated and thus converted into the neuv 
tral salt : — 

2 NaHCO, = C0 2 + H 2 + Na 2 C0 3 ; 

and the carbon dioxide given off is used for the purpose of satu 
rating the ammonia contained in the original solution. Tht 
ammonium chloride obtained in the second stage of the process 
is decomposed either by lime, CaO, or magnesia, MgO, and the 
ammonia thus recovered. This process is also known as 



sodium. 333 

the Solvay process, as its introduction is due to the exertions 
of M. Solvay. 

Soda Crystals, or Sal Soclae, much used in softening hard 
water, are obtained by dissolving soda-ash in water, and allow- 
ing the crystals to deposit from a saturated solution. These 
crystals possess the formula Na 2 C0 3 + 10 H 2 0. 

Acid Sodium Carbonate, NaHC0 3 , can be obtained from 
soda crystals by allowing them to be acted upon by C0 2 gas. 
This substance is known as Bicarbonate of Soda, and is 
employed in medicine and for preparing effervescing drinks. In 
domestic economy it is used as Saleratus and as an ingredient 
of Baking Powder. 

(J) Silicates. Glass is a silicate of calcium and either 
sodium or potassium. Ordinary glass contains sodium. The 
difficultly fusible Bohemian glass contains potassium. For 
some purposes, lead is introduced instead of calcium. Glass 
made in this way, having a high refractive power, is very use- 
ful for optical purposes. Ordinary glass is made by melting 
together quartz and quicklime or calcium carbonate and sodium 
carbonate. 

(7c) Man}' other salts of sodium may be obtained in the 
shops, and are very useful in preparing test solutions, especially 
when the student is working for acids in the non-metals. 

364. Tests for Sodium. — 1. Sodium compounds color 
the non-luminous flame intensely yellow, and this color is 
obscured by the blue glass. 

Note. Any substance, as dirt on the platinum wire, will give this test 
for sodium. Therefore, clean the wire carefully, and convince yourself 
that the color is not caused by the ordinary impurities. Try some known 
sodium compound till you recognize the flame. 

2. The sodium spectrum gives two intense lines in the 
yellow which lie so close that they often seem but one. 
They coincide with Fraunhofer's D lines in the solai 
spectrum. 



334 AMMONIUM. 

AMMONIUM. 

Symbol, NH 4 . — Molecular Weight, 18. 

365. When sodium amalgam containing one to three 
per cent of sodium is thrown into a strong solution of 
ammonium chloride, a curious spongy substance is formed, 
which gradually rises in the vessel, filling a large amount 
of space. It is very unstable, giving off ammonia and 
hydrogen, and leaving metallic mercury. This substance, 
according to the most careful examinations, contains nitro- 
gen and hydrogen in the proportions indicated in the for- 
mula NH 4 , and this is simply in combination with mercury. 
As this group plays the part of a metal in the salts 
obtained from ammonia and the acids, — as in (NH 4 )C1, 
(NH 4 )N0 3 , (NH 4 ) 2 S0 4 , etc., — it is called ammonium, and 
the compound with mercury, ammonAim amalgam ; hence, 
further, the salts obtained with ammonia are called ammo- 
nium salts. The metal ammonium, NH 4 , is, however, 
hypothetical. 

OF THE AMMONIUM SALTS AVE NOTICE: — 

(a) Ammonium CTdoride, or Sal Ammoniac, NH 4 C1, which 
occurs as a natural deposit, but is now prepared from the 
ammoniacal liquors of gas works. The ammonia gas is liber- 
ated from the gas liquors by adding slaked lime, and is led into 
a dilute solution of hydrochloric acid, from which this salt is 
obtained by evaporation ; the chloride is afterwards purified by 
sublimation. This salt is used as a reagent and as a source of 
ammonia in the laboratory, and as an important aid in solder- 
ing, welding, etc. 

(h) Ammonium Nitrate, NH 4 N0 3 , is used as a source of 
Laughing Gas or Nitrous Oxide, and can be prepared by neu- 
tralizing nitric acid with ammonia. 



THE RARER METALS OF THE FIFTH GROTJF. 335 

(c) Sodium- Ammonia /)l Phosphate, or Microcosmic Salt, 
HXaXHJP0 4 -f 4 HX), is much used in blow-pipe work, since 
it forms a colorless bead on the platinum wire, and receives a 
color by adding certain substances. It is formed by the decom- 
position of urine, and is artificially prepared by dissolving five 
parts of sodium phosphate with two parts of ammonium phos* 
phate in hot water, and allowing the solution to cool. 

(d) Ammonium Carbonate, (NH 4 ) 2 C0 3 , is used as a group 
reagent, and is now prepared by subliming CaC0 3 with ammo- 
nium sulphate, and digesting the product formed with strong 
aqua ammoniae. 

(e) Ammonium Sulphide, (NH 4 ) 2 S, is used as a group 
reagent, .and is very unstable, passing into (XH 4 ) 2 Sx upon 
exposure. This reagent is readily prepared in the laboratory 
when needed by passing a current of hydrogen sulphide gas 
into aqua ammoniae until the solution will not precipitate mag- 
nesium sulphate. 

366. Tests for Ammonium. — The tests for ammonium 
have already been given (Art. 55), and it only remains 
to add that, in the course of analysis, although the ammo- 
nium salts remain in the fifth group, it is necessary to 
apply these tests directly to the original solution. 

THE RARER METALS OF THE FIFTH GROUP. 

LITHIUM. 

Symbol, Li'. — Atomic Weight, 7. 

367. Lithium is a rare metal which is found in Lepido 
lite, Triphylline, (Li,Xa) 3 P0 4 + (Fe,Mn) 3 P0 4 , and some 
other minerals. This metal occurs in most surface waters 
and in many mineral waters, and easily finds its way into 
the animal and vegetable kingdom?. 



336 RUBIDIUM, — CESIUM. 

It is prepared by electrolyzing its chloride, and is a 
silver-white metal, readily oxidizing in the air. 

The principal salt is the carbonate, which is used in 
medicine. The chloride, nitrate, sulphate, etc., can be 
prepared by treating the carbonate with the proper acid. 

Query. Why are the carbonates of the metals chiefly employed in 
preparing the rarer salts ? 

368. Tests for Lithium. — 1. Lithium compounds color 
the flame intensely crimson ; this color is obscured only by 
very thick blue glass. 

2. The spectrum of lithium affords a certain test, 3 r ielcling 
the bright-red line, Lia, and the weak yellow line, hi/3. 

RUBIDIUM. 
Symbol, Rb'. — Atomic Weight, 85.5. 

369. Rubidium is prepared like potassium, which metal 
it closely resembles. It is widely distributed, but occurs 
only in very minute quantities. It is found in Lepidolite, 
Triphylline, Mica, Orthoclase, and other minerals, as well 
as in various waters and soils. 

Rubidium is detected by its coloring the flame some- 
what more red than potassium, but more certainly by its 
spectrum, which yields two violet lines, Rba and Rb/3. 

CiESIUM. 

Symbol, Cs 7 . — Atomic Weight, 133. 

370. Caesium is the first metal discovered by the spectro- 
scope, and occurs with the other alkali metalso It has not 
been prepared, but its salts are known. 

Ccesium is detected by its spectrum, which yields the 
bright-blue lines, Csa and Cs/3. 



DETECTION OF THE FIFTH GEOUP METALS. 337 

371. Detection of the Fifth Group Metals. — 1. Test 
the original solution for ammonium. 

2. Free the solution from the first four groups (magne- 
sium excepted) by adding NH 3 , NH 4 C1, and (NH 4 ) 2 C0 3 ; 

the filtrate is to be tested for Na, K, and Li ; accordingly, 
evaporate the solution nearly to dryness, and proceed 
thus : — 

Qd) The sodium flame is to be observed by the naked 
eye, and Is intensely yellow. 

Note. Remember that traces of sodium are usually present. 

(5) Sodium obscures the violet potassium flame, but the 
potassium flame becomes visible when observed through 
the blue glass which shuts off the sodium color. 

(c) The lithium flame is readily determined by its crim- 
son color. It is obscured only by very thick blue glass. 
The lithium flame is visible even when Na and K are 
present. 

General Note. The student is not to infer that the analytical grouping 
of" the metals or the numbering of the groups is otherwise than purely 
arbitrary. Many different groupings can be made, depending upon the 
reagents employed in the course of analysis. The following table will 
enable the student to compare the grouping and numbering used in this 
book with those used by Fresenius : — 

I K, Na, NH 4 , Li V. 

II Ba, Sr, Ca, Mg IV. 

HI Al, Cr ) 



IV.... Zn, Mn, Ni, Co, Fe 

V. 

VI 



\ Ag,Hg,Pb : I. 

I Bi,Cu, Cd I n 

As, Sb, Sn S 



The Roman numerals in the first column indicate the groups given in 
Fresenius. 

372. To Analyze an Unknown Solution. — In making 
a complete qualitative analysis of an unknown solution, it 



338 



TO ANALYZE AN UNKNOWN SOLUTION. 



is desirable to proceed by a methodical plan. From what 
has preceded, it is evident that the first step should be to 
determine the bases; this may be accomplished as indi- 
cated in the following table. When we know what bases 
are present, we are then prepared to determine the acids. 
In case we obtain arsenic, chromium, manganese, etc., we 
know that these elements are apt to be present as acids. 
Accordingly we first try for the acids formed by those 
elements. In case these elements are not present, we 
remove the bases by E (as explained farther on), and then 
test for acids as in Art. 227. 



A. 

The solution may contain a salt of i — - 



1. 


Pb, Ag, or Hg' 


2. 


Hg, Cd, Pb, Cu, 
Bi, As, Sb, Sn 


3. 


Fe, Cr, Al, Zn, 

Mn, Ni, Co.... 


4. 


Ba, Sr, Ca, Mg 


5. 


K, Na, NH 4 , Li 



The precipitates : - 



+ HC1 = FhC \ Al£l, HgCl ( Solutions of 2, 3, 4, 
white white white ( and 5. 



Filter out the precipitate, and proceed by Art. 247. 
Treat the nitrate by B. 



Hg, Cd, Pb, Cu, 

Bi, As, Sb, Sn 



Fe, Cr, Al, Zn, 
Mn, Ni, Co.... 



B. 



Filtrate from A , — 



Ba, Sr, Ca, Mg 



Na, K, NH 4 , Li 



The precipitates : — 



f As 2 S 3 Sb 2 S 3 , Sb 2 S, SnS SnS. 2 PbS 



Kh,sh 



I yellow ' orange brown yellow black 



Bi 2 S 3 CuS CdS HgS 



{ black black yellow black 



( Soluti 
1 3,4,; 



Solutions of 
and 6. 



Filter out the precipitate, and proceed by Art. 278. 
Boil the filtrate to expel H 2 S, and add a little HN0 3 , and boil a short 
time to oxidize ferrous to ferric salts, and then proceed by C. 



TO ANALYZE AN UNKNOWN SOLUTION. 339 

Co 

Filtrate from B : — The precipitates : — 



3e 


Fe, Cr, 
Mn, Ni 


Al, Zn, 
,Co.... 


4 


Ba, Sr, 


Ca, Mg 


5 


Na, K, 


NH„ Li 



+ NH 3 + NH 4 C1 = Fe (° H )» , Cr (° H )b , A1 (OH), + 

reddish brown bluish green white gelatinous 

Solutions of Zn, Mn, Ni, Co, 4, and 5. 
Filter out these precipitates, and proceed by Art. 303. 

(Tothefiltrate)+(NHJ 2 S = i^ ) 9?§, ™ M + 

flesh col. black black white 

Solutions containing 4 and 5. 



Filter out this precipitate, and proceed by Art. 321. 
Boil the nitrate to expel H 2 S, and proceed by D. 

D. 

Filtrate from C : — The precipitates : 
1 



Ba, Sr, Ca, Mg . 

)- + NH 3 +NH 4 C1+(NHJ 2 C0, =---», *™h, ^^h + 

Na, K, NH 4 , Li 3 i i2 ? white white white 

Mg and 5. 

Filter out these precipitates, and proceed by Art. 355. 

Divide the nitrate in two parts ; to one of these parts add Na 2 HP0 4 : 

MgNH 4 FO, 
precipitate, wMte 

Test the second part by Art. 371 for 5. 
Test for acids by E. 

E. 

1. If the solution contains arsenic, chromium, or manganese, etc., test 
the solution for the acids formed by these elements. 

2. When the solution contains only the metals of the fifth group, test 
the original solution directly for acids, following the directions under 
Art. 227, and as given under each acid in the non-metals. 

3. When other metals, not acid forming, are found, it is best to make 
the solution neutral with KOH, and then to add K 2 C0 3 to precipitate them. 
Filter out the precipitate, and test the filtrate. In case calcium super- 
phosphate be present, the phosphate will be found in the precipitate. 

Now, since we have added a carbonate, the filtrate contains the added 
carbonate. In consequence of this, we must test the original solution for 
carbonates. Before proceeding as in Art. 227, it is best to remove the 
added carbonate by means of HC1 ; in this way we get a solution which 



340 TO ANALYZE AN UNKNOWN SOLUTION. 

may be tested for all the non-metallic acids excepting HC1. We may pre- 
pare another portion of the filtrate containing the added carbonate by 
adding HN0 3 ; this solution is to be tested for HC1. 
Test for some Organic Acids given under F. 

F. 

1. Tartaric Acid, H 2 (C 4 H 4 6 ), is detected by adding AgN0 3 to the nor- 
mal solution ; a white precipitate is thrown down, which turns black on 
boiling. And further, when tartaric acid is ignited, it gives off the odor of 
burnt sugar. CaCl 2 gives a white precipitate, Ca(C 4 H 4 6 ), soluble in cold 
solution of KOH. 

2. Acetic Acid, H(C 2 H 3 2 ), forms a red solution with Fe Cl 3 , which is 
not decolored by adding HgCl 2 , while red KCyS solutions with Fe Cl 3 are 
thus decolored. 

Also, when warmed with sulphuric acid and a little alcohol, acetic acid 
gives off the odor of acetic ether. 

3. Citric Acid, H 3 (C 6 H 5 7 ), gives a white precipitate with AgN0 3 , which 
does not blacken on boiling; also it gives a white precipitate with lead 
acetate. Further, concentrated nitric acid produces from it acetic and 
oxalic acids. 

4. Oxalic Acid, H 2 C 2 4 , is decomposed into C0 2 and CO by H 2 S0 4 . 
When treated with CaCl 2 , the oxalates give a white precipitate, soluble 

in HC1, insoluble in acetic acid. (See Art. 227.) 



APPENDIX. 



APPENDIX. 



THE LABORATORY. 

1. The Room selected for the chemical laboratory should be drv 
well lighted, and well ventilated. Generally an upper room is preferable 
to a basement ; basements are apt to be damp, and poorly lighted, and 
the laboratory fumes are not so easily restrained from diffusing them- 
selves through the building ; with proper precautions, however, little or no 
inconvenience will arise from the use of a dry, well ventilated basement 
room. 

It is desirable that the rooms devoted to chemistry and physics should 
be adjacent to each other, as many pieces of apparatus will illustrate 
portions of both studies. If communication between the two rooms can 
be secured by sliding doors, so much the better ; this arrangement offers 
many advantages in those schools where chemistry and physics are taught 
by the same teacher. In case the rooms cannot be adjacent, they should 
be as near together as possible. 

GENERAL FIXTURES. 

In case the building is heated by steam, and lighted by gas y many of 
the general fixtures are easily provided. 

2. The Condenser for procuring distilled water may be connected 
directly to the steam-pipes used in heating the building. A plain sheet 
copper cylinder 30 cm in diameter, and 135 cm high, will afford all the 
distilled water thirty students will require : this cylinder simply needs 
a faucet at the bottom, through which the water may be drawm when 
needed, and a small pet-cock at the top, through which the air is to be 
blow r n out when the steam is first turned on. The steam is admitted 
at the top of the cylinder which stands upright, and which needs no 
mternal coil nor external jacket. The cylinder should be able to carry 
all the pressure that the boilers are likely to put upon it, and it may stand 
in any convenient part of the room, as no hissing or other disagreeable 
noise is heard. 



844 APPENDIX. 

In case the building does not contain steam, permission may be 
obtained from some factory or mill to connect such a condenser to the 
boilers used there. The connecting pipe should be as small as possible, 
and the steam should be allowed merely to leak through the valve, by 
means of which the condenser is shut off from the boiler. 

Many other devices are to be had, some of which are applicable under 
one condition, while under other conditions another device may succeed 
more satisfactorily, e.g. 

Small quantities of distilled water are to be had by means of a Liebig 
condenser, in connection with a still heated by a gasoline stove, or by an 
ordinary stove ; a coil may be passed through a cask containing cold 
water, etc., etc. 

One fact should be noted here ; ordinary rain-water, and water as 
usually prepared by distillation, usually contain free ammonia. Water free 
from ammonia may be obtained as explained in App. 77. 

3. The Tank for Wash- Water may be placed in a corner of the room, 
and its bottom should be four or five feet higher than the faucets from 
which the water is drawn. Pipes leading from the tank may carry the 
water to a sink and to each student's desk. 

Pure cistern water is best for ordinary washing purposes in a labor- 
atory ; the water may be raised to the tank by a force-pump, or a cistern 
may be constructed under the roof of the building. 

4. A Gas Chamber is useful for many purposes. It may be built of 
sash with glass, and it may stand in any convenient place, so that it may 
be connected to a good ventilating shaft. By means of such an arrange- 
ment, the operator can observe what is taking place, and the unwhole- 
some gases generated are carried out of the building. It is convenient to 
have two or three separate apartments not in communication with one 
another, and each one with a separate door. The size of such a chamber 
will depend upon the requirements of the school, but one 3 ft. square X 6 ft. 
high will answer for most small laboratories. 

5. Cases for chemicals, apparatus, etc., are convenient and inexpen- 
sive. It is desirable to have a portion of the case provided with sash 
doors, and the remainder is to be cased with panel doors, thus providing 
dark closets in which stock chemicals and reagents may be kept to better 
advantage. 

6. Working Tables may be placed against the walls of the room, or 
through its centre. A table 15 ft. long, 3 ft. 1 in. high, and 3 ft, 4 in. 
wide, and standing from the walls, will afford ample room for eight 



APPARATUS FOR STUDENT'S DESK. 845 

students to work at a time. If the class be divided into two working 
divisions, such a table will accommodate sixteen students, while the 
apparatus per student will thereby be materially lessened. In the centre 
of the table are placed four desks, while sink-bowls are placed between. 
One side of such a desk is shown in the Frontispiece ; this cut is taken 
from the photograph of a desk in Ypsilanti High School Laboratory. In 
the table just under the desk is a drawer, used by the student to keep his 
apron and other personal property which he requires in his work. 

The tables may be supported by legs or by square posts ; in the latter 
case, cupboards may be constructed under the tables ; but in case cup^ 
boards are made, a bottom or an extra floor should be put in, so that the 
base-board under the doors may not form an obstruction in sweeping out 
any dust, etc., that may collect in the cupboard. 

The dimensions of the desk shown are as follows : Height, 2 ft. 4 in. ; 
length, 2 ft. 6 in. ; breadth at bottom, 14 in. ; at top, 12 in. ; space under- 
neath first shelf, 11 in. ; second space, 8 in., and third space 6 in. The 
top of the desk may be utilized as a shelf. A partition through the desk 
divides it into halves, thus forming two working cupboards, one on each 
side of the desk. 

The gas chamber, tables, desks, and cases, can be made by any car- 
penter. 

APPARATUS AND REAGENTS. 

In considering the materials under this heading, it will be convenient to 
follow the order : — 

(a) Apparatus for the student's desk ; 

(b) Reagents for the student's desk; 

(c) Reagents for the side table ; 

(d) Working material; 

(e) General apparatus for the laboratory. 

APPARATUS FOR THE STUDENT'S DESK. 

Perishable apparatus, such as glass and porcelain ware, should be kept 
in stock in Order to supply quickly any loss by breakage, etc. 

7. Test-Tubes. — At the start the student should have twelve 4-in. test- 
tubes, and two 8-in. test-tubes of a larger diameter. The latter are to be 
fitted with rubber stoppers pierced with one hole, through which is inserted 
a bent delivery-tube; they are used as generators. 

Test-tubes are perishable, but they are not expensive. A liquid may 



346 APPENDIX. 

be heated in a test-tube by placing the tube directly in the Bunsen or 
alcohol flame, provided the flame does not strike the tube at the upper 
level of the liquid. 

When heating a substance in a test-tube, the student should never hold the 
mouth of the tube towards himself nor towards others, since any explosion, as 
of steam or other gases, might result seriously ; it is best to move the test- 
tube gently through the flame when heating any substance. 

With a little practice the student may mend a test-tube, the bottom of 
which has been broken. To accomplish this, the tube is first to be cleaned 
and dried ; the broken end is then strongly heated in the Bunsen flame 
until the glass becomes soft ; the broken edges of the tube are now forced 
together by means of a bit of glass tubing ; when the bottom is closed, 
the end of the tube is freed from unnecessary material by carefully draw- 
ing out the highly heated end of the tube with the glass rod ; the end of 
the tube is now strongly heated until it becomes somewhat thicker than 
the walls of the tube; now the mending is to be finished by blowing gently 
into the tube, in order to give the end a rounded form. When heating the 
tube, it should be rolled over constantly in the flame, so that all sides may 
be heated alike. An alcohol or gas blast-lamp may be used to good advan- 
tage for this work, and for such other glass-work as usually must be done 
in the laboratory. 

8. Hard Glass Tubing. — Each student should have a tube 8 in. long, 
and with a bore of about J- in. ; this is used for heating solids as in 
Exp. 3 p. 

A hard glass test-tube has been mentioned in the text. These are more 
expensive than ordinary test-tubes; for most purposes mentioned a com- 
mon tube may be used, but it is almost invariably ruined ; this is of no 
great moment, however, if a tube that has been mended is employed. 

9. A Test-Tube Rack for holding test-tubes is shown in the Frontis- 
piece. The student can make this for himself by taking a suitable block 
of wood and setting in one edge of it a row of wooden pins 3 in. high; in 
the other edge holes arc bored, which will serve to hold tubes containing 
liquids. 

10. A Test-Tube Swab for washing out test-tubes is also to be made 
by the student. It is simply a wooden stick as large as a lead-pencil, upon 
the end of which a bit of sponge is fastened. 

Test-tube brushes of various designs are also to be had in the market, but 
the swab will answer for nearly every purpose. 

11. A Glass Stirring-Rod may be made from suitable solid glass rods 



APPARATUS FOPv STUDENT'S DESK, 347 

which are to be kept in the laboratory. This rod should be about as large 
and long as a common slate-pencil. The. ends of the rod must be melted 
smooth and round in the Bunsen flame. 

12. Platinum Wire and Platinum Foil are much used. The wire 
should be about 3 in. long, and one end of the wire should be fused into a 
short glass tube; the other end of the tube should be closed. The plat- 
inum foil may be about 1 in. X J in. The uses of these articles are 
described in the text in the appropriate places. 

13. A Blow-Pipe of the form shown in the Frontispiece (Bp), known 
as Black's, is the best of the cheaper forms. A blow-pipe should last 
many years. 

14. Steel Tongs (T in Frontispiece) are useful to handle hot evap- 
orating dishes, hot crucibles, etc. The student may readily hold a test- 
tube while boiling solutions, etc., by putting a narrow strip of cloth around 
the upper end of the tube and clasping the ends of the strip in these tongs. 
These tongs should last five or six years. 

15. Funnels are shown in Fn ; these are of glass. The student 
should have two, — one 2 in. and one 3 in. or 4 in. in diameter. The fun- 
nels should have their stems ground off at an acute angle to facilitate the 
process of filtration. Funnels are seldom broken. 

16. Filter-Papers should be cut round, and should be furnished the 
student in packages. The proper size papers for the funnels are 4 in. and 
6 in. in diameter. These papers should be kept in a tin box of prope. 
form and size. 

The filter-papers are placed in the funnel as follows : First, they are 
folded through the centre ; then another fold, at right angles to the first, 
is made, which leaves the paper in the form of a sector of a circle ; now, 
by inserting the apex of the sector into the funnel, the paper may be 
opened out in form of a cone that will fit the funnel. It will be seen that 
two pockets are formed in the paper, either of which will serve as a recep- 
tacle for the fluid to be filtered. It is best to wet the paper with distilled 
water before filtering a solution containing a precipitate, as this tends to 
prevent the precipitate from adhering so closely to the paper. 

Beginners are often at a loss as to how they may divide small precipi- 
tates into several parts ; this may be accomplished in different ways, of 
which these two are as convenient as any : First, the point of the filter- 
paper containing the well-washed precipitate may be pierced, and the damp 
precipitate may be washed through into a beaker glass by means of dis- 
tilled water; the precipitate may now be agitated with a stirring-rod 



348 APPENDIX. 

until it is suspended in the water, when portions of it may be poured out , 
Second, the precipitate may be left on the filter-paper, and whether damp 
or dry may be separated into portions by tearing the filter-paper into the 
requisite number of parts. If the precipitate be damp, it may be washed 
off each part as needed, by means of water. If the precipitate be dry, and 
the student wishes to dissolve the dried precipitate, he may put the paper 
and all in a test-tube, and after dissolving may remove the particles of the 
filter-paper by passing the solution through a new filter. 

For filtering acids a little spun glass is best; this may be crowded down 
into the stem of the funnel, and after passing the acid through it may be 
washed and preserved for further use. 

17. Generating Flasks, one each of 2-oz. and 4-oz. capacity, will 
answer for the student's needs. These flasks are used for generating gases, 
etc., and are fitted with delivery-tubes as shown in the Frontispiece, F. 
These flasks are sometimes broken. 

18. Two Beaker Glasses (see Bk in Frontispiece), one of 2-oz. and 
the other of 4-oz. capacity, are needed. In them solutions are boiled, 
crystals are allowed to form, and solutions for working purposes are kept 
temporarily, etc., etc. Neither these beakers nor the Florence flasks men- 
tioned in 17 should be heated in the naked Bunsen flame. They should 
always be placed on wire gauze or on a sand-bath. 

19. Evaporating Dishes (see E in Frontispiece), one each of about 
3-oz. and 4-oz. capacity, are needed. These should be heated on the sand- 
bath or on wire gauze. They are seldom broken. Prof. Weitbrecht's stu- 
dents frequently use saucers as evaporating dishes. 

20. A Bunsen Burner is shown at B. The use of this has been ex- 
plained. In laboratories not containing gas for heating purposes, alcohol 
lamps are the best substitute. In nearly every place in the text where 
" Bunsen flame " has been used, " alcohol flame " may be substituted. 

21. A Wash-Bottle, or " Blow-Bottle " as it is familiarly termed by 
students, is shown at W in Frontispiece, as made by a student from whose 
desk this cut was taken. Each student can make his own bottle ; the de- 
livery-tube should be drawn out into quite a fine jet, so that the stream of 
water issuing from it, upon blowing into the mouth-piece, shall be quite 
small. 

22. Each Student should provide himself with a toy magnet, a clay 
tobacco pipe for blowing soap-bubbles, a sponge, a towel, a bundle of soft 
white rags, a box of matches, a watch-crystal, an oil-cloth apron, and a 
pair of rubber sleeves. The uses of these are too evident to need men- 
tioning. 



APPARATUS FOR STUDENTS DESK. 349 

23. A King Stand is shown at A. This is used to support funnels 
while filtering, and sand-baths, retorts, generating flasks, etc., while heat- 
ing. The rings may be removed or clamped in any position upon the 
upright standard. 

24. A Blue-Glass is shown at G. This is a frame containing two thick- 
nesses of glass. One blue-glass will answer for two desks. 

25. A Sa nd-Bath is shown at S, resting on a ring. This is a saucer- 
shaped sheet-iron dish, which may be hammered out by any tinsmith. It 
must be large enough to rest on the largest ring. The dish is filled with 
clean white sand, and in this sand beakers, evaporating dishes, etc., are 
set ; the heat is applied to the sand-bath. There is one objection to a 
sand-bath, — the sand is apt to get scattered on the student's desk and find 
its way into the waste pipes leading from the sink-bowls. It is safer, how- 
ever, to heat glass ware, etc., in a sand-bath than it is on a 

Wire Gauze. This gauze is of fine brass wire, and is placed between 
the flame and the evaporating dish. It will be found to be neater and less 
objectionable in several respects than the sand-bath, but it is not quite so 
safe to heat fragile ware upon it. 

Professor Foote recommends asbestos paper in place of the sand-bath 
and wire gauze. 

26. A Match-Safe should be furnished to each desk, and the student 
should not be allowed to put matches in his drawer. Employ sulphur 
matches ; parlor matches are too dangerous. 

27- If the student is to do a little quantitative work, he will need, in 
addition to the foregoing, a porcelain crucible with cover, a feather, a 
sheet of glazed paper, and a triangle made by joining three common clay 
tobacco-pipe stems by means of iron wire. 

28. Litmus Papers. These papers may be purchased ready for use, 
or they may be prepared in the laboratory by dipping sheets of bibulous 
paper in litmus solution ; the papers thus prepared are blue. Red and blue 
papers are needed ; the red papers may be prepared by moistening the blue 
papers in dilute acetic acid. The papers should be cut into strips 4 cm 
long and 4 mm wide ; they may be kept in a bottle or cardboard box. 

29. Charcoal. A fine variety of charcoal is to be purchased of chem- 
ical dealers, but selected pieces may be obtained from ordinary charcoal 
that will answer all purposes. Charcoal should not be kept in the drawers 
or on the desk. Separate pans with legs should be provided to avoid dan 
ger from fires. 



85U APPENDIX. 

The reagents for the student's desk should be kept in stock in the lab- 
oratory, i.e., a sufficient quantity of the dry salts and of the liquid reagents 
should be purchased at the beginning of the year to last throughout that 
year. Some of these reagents are more convenient in a dry form ; but 
most of these are used in the form of solutions. 

The solutions should be kept in good glass-stoppered bottles, holding 
J 1 or 4 oz., similar to those shown in the Frontispiece. It is desirable that 
these bottles have permanent acid-proof names and symbols. 

The dry salts should be kept in small 2-oz. salt-mouth bottles, and 
these are best when provided with glass stoppers. 

A few words of caution concerning the care of reagent bottles are in 
place here. A good reagent bottle must have its stopper ground to fit it, 
and this stopper will not fit any other bottle in the set. Consequently the 
stoppers should never be interchanged. Again, the stoppers of all re- 
agent bottles, excepting sulphuric acid, should be paraffined with gum- 
stock paraffin, otherwise they are quite apt to stick ; often the bottles are 
ruined or cracked by trying to remove the stoppers. There is no excuse 
for breaking a reagent bottle. The solutions should not be allowed to 
freeze, as the bottles may thus be broken. 

The student should not lay down the cork of a reagent bottle while 
pouring out a solution, since he may thus change stoppers with his bottles 
or contaminate his reagents. Again, no solution but the one correspond- 
ing to the name on the bottle should ever be placed in a reagent bottle. 

Another important item is that each bottle have a place on its shelf, 
and always be put in its place ; thus the student comes to know where to 
find a reagent, just as a printer knows where to find the letters in his case. 

Since some order must be followed, that in which the reagents are 
described below may be insisted on. Commencing with the first name in 
the list on the upper shelf, left-hand side, arrange the bottles toward the 
right ; and, when the shelf is full, begin again on the left-hand of the next. 

Since systems of nomenclature vary somewhat, and since labels and 
names are apt to vary decidedly, all the names are given in connection 
with each reagent, the most preferable coming first, the symbol next, and 
thereafter the various other names, in order of their preference, excepting 
the name given in italics, which is that of the United States Pharmaco- 
poeia ; its position has no reference to its preferment. 

In naming the acids, the common names are given first, for the reason 
that these names are good ones, and in spite of all attempts to do away 
with them, they still persist in remaining ; and it is perhaps but wise to 
submit to the inevitable. Thus, that acid whose formula is H 2 S0 4 , is 
called sulphuric acid ; hydrogen sulphate, for some reasons, would be better, 



LIQUID REAGENTS. 351 

but the change is not universally accepted. Again, hydric sulphate has 
^een proposed, but this is still less favorably received ; while the oldest 
name of all, oil of vitriol, is scarcely used or known by the last generation 
of chemists, though still retained by manufacturers. 

The reagents enumerated below (with a few exceptions, which are 
noted) should be chemically pure. Of all persons, a beginner should have 
the best materials to work with ; moreover, good material is now so cheap 
that there is neither profit nor sense in using goods of a poor quality. 

LIQUID REAGENTS. 

30. Sulphuric Acid, H 2 S0 4 ; Hydrogen Sulphate; Hydric Sulphate ; 
Dihydric Sulphate; Oil of Vitriol; Acidum Sulphuricum. 

This acid should be bought in a concentrated form, sp. grav. 1.843, and 
should be dealt out to students in this form; it should evaporate on plati- 
num foil without leaving any residue, and it should be colorless. 

The commercial acid may be contaminated with arsenic, antimony, iron, 
aluminum, calcium, potassium, sodium, lead, magnesium, hydrochloric 
acid, nitrous acid, nitric acid. 

31. Nitric Acid, HN0 3 ; Hydrogen Nitrate ; Hydric Nitrate ; Aqua 
Eortis ; Acidum Nitricum. 

This acid may be bought in a concentrated form, and afterward re- 
duced with water to reagent strength, which is 32 per cent acid, sp. grav- 
1.32. (See 34 for computation.) 

Pure nitric acid is colorless, but, on standing exposed to the light, it 
may become colored by the lower oxides of nitrogen, which, as a usual 
thing, are not harmful. They may be removed by passing a current of air 
through the acid by means of a glass tube attached to a hand-bellows. 

The commercial acid may contain calcium, sodium, iron, oxides of nitro- 
gen, hydrochloric acid, sulphuric acid. 

32. Hydrochloric Acid, HC1 ; Hydrogen Chloride ; Hydric Chloride ; 
Muriatic Acid ; Chlorhydric Acid ; Chlorhydrate ; Spirit of Salt ; Acidum 
HydrochJoricum. 

This acid may likewise be purchased in a concentrated form, and after- 
wards reduced to the reagent strength, 24 per cent acid, sp. grav. 1.12. 
The pure acid is colorless, and leaves no residue upon evaporation ; upon 
standing, it may become colored by free chlorine. 

The commercial acid may contain iron, sodium, aluminum, arsenic, sul- 
phuric acid, sulphurous acid. 

33. Acetic Acid, H(C 2 H 3 2 ); Hydrogen Acetate; Hydric Acetate 
Acidum Aceticum. 



352 APPENDIX. 

Since acetic acid is not so extensively used as the preceding acids, it 
may be purchased of a reagent strength, 30 per cent acid, sp. grav. 1.04. 
The pure acid is colorless, and leaves no residue upon evaporation. 

The commercial acid may contain sodium chloride, lead, copper, iron, 
empyreumatic substances, sulphuric acid, sulphurous acid, nitric acid- 

34. Ammonia, NH 3 . The reagent solution contains 10 per cent of the 
gas NH 3 , and has a sp. grav. 0.96. It is prepared from the " Stronger 
Water of Ammonia," or Aqua Ammonia (28 per cent gas; sp. grav. 0.90; 
(J. S. P.), by the addition of distilled water. The concentrated form is 
more convenient to keep in stock, as it requires less space for storage. In 
the case of ammonia, and of the concentrated acids previously mentioned, 
the label of the original package should state the per cent and sp. grav. 

Commercial aqua ammonia may contain ammonium chloride, ammonium 
carbonate, calcium sulphate, empyreumatic material. 

The amount of water to be added to a given volume of a stronger solu- 
tion may be determined by calculation. Thus, in the case of ammonia: 
We know that l 1 of the strong solution weighs 900=, and that 28 per cent 
of that weight, or 252s, is NH 3 . It is evident that this 252s is to form 
10 per cent of the weight of the reagent solution ; hence, the whole weight 
of the reagent solution will be 252 -f- .1 = 2520=. Now, we already have 
taken 900s of the strong solution ; consequently 2520 - 900 = 1620s, or 
the weight of distilled water to be added to l 1 or 1000 cc of the strong 
solution. It is further evident that one part, by volume, of the strong 
solution requires 1.62 parts, by volume, of distilled water. 

35. Ammonium Carbonate, (NH 4 ) 2 C0 3 ; Carbonate of Ammonia; Am- 
nionic Carbonate ; Volatile Salt ; Ammonii Carbonas. 

This solution is prepared by dissolving 1 part by weight of the dry salt 
in 4 parts by weight of water, after which one part of reagent ammonia 
solution is added. 

The commercial salt may contain calcium, iron, lead, chlorides, iodides, 
sulphates. 

It is not necessary to weigh the water, since l cc of water weighs Is. 
The graduated ware used in measuring solutions is graduated at a certain 
temperature, usually 15° C. When accuracy is required, the temperature 
of the water or of the solution to be measured should be that at which the 
apparatus is graduated. 

36. Ammonium Sulphide, (NHJ 2 S ; Sulphide of Ammonium ; Am- 
nionic Sulphide. 

This solution may be purchased ready for use, or it may be prepared in 



LIQUID REAGENTS. 35£ 

the laboratory by passing hydrogen sulphide gas through a reagent solu- 
tion of ammonia until the solution no longer precipitates magnesium 
sulphate. This reagent changes, upon standing, to the yellow variety. 
Although the formula of the yellow ammonium sulphide has been given 
as (NH 4 ) 2 S 2 , its composition varies greatly. 

37. Ammonium Chloride, NH 4 C1; Chloride of Ammonium; Am- 
nionic Chloride ; Muriate of Ammonia; Sal Ammoniac; Ammonii Chloridum. 

To prepare this reagent solution, dissolve 1 part of the crystallized salt 
in 8 parts of water. 

The commercial salt may contain iron, sulphates, organic matter. 

38. Ammonium Oxalate, (NHJ 2 C 2 4 ; Oxalate of Ammonium; Am- 
nionic Oxalate. 

This is prepared by dissolving the crystallized salt, (NHJ 2 C 2 4 + H 2 0, 
in 21 parts of water. 

The commercial sail may contain sodium, potassium, calcium, aluminum, 
lead, sulphates, nitrates. 

39. Potassium Hydroxide, KOH ; Potassium Hydrate ; Potassic 
Hydrate; Caustic Potash. 

This solution is prepared by dissolving 1 part of the dry sticks in 20 
parts water. It is not absolutely essential that this salt be strictly C. P. ; 
there is a good white article ("rein weiss^) containing a little silica, and 
perhaps a trace of chlorine, that will answer most purposes, and it is much 
cheaper than the C. P. article. 

The commercial article may contain iron, aluminum, sodium, calcium, or- 
ganic matter, silica, chlorides, sulphates, carbonates. 

44'. Sodium Hydroxide, NaOH, is preferred by many chemists to 

potassium hydroxide, since the former is much cheaper. This solution is 
made by adding 1 part of the fused substance to 9 parts water. The im- 
purities are much the same as in the potassium compound. 

40. Potassium Carbonate, K 2 C0 3 ; Carbonate of Potassium; Potas- 
sic Carbonate ; Carbonate of Potash (potassa) ; Potassii Carbonas. 

Make this solution by dissolving 1 part of the dry salt, K 2 C0 3 + 3H 2 
in 10 parts water. 

The commercial article may contain iron, aluminum, silica, sodium, chlo- 
rides, sulphates, sulphides. 

41. Potassium Iodide, KI; Iodide of Potassium; Potassic Iodide,: 
Potassii Iodidum. 

Dissolve 1 part of the salt in 20 parts of water. 



354 APPENDIX. 

The commercial article may contain sodium, iodates, sulphates, chlorides, 
carbonates. 

42. Potassium Bichromate, K 2 Cr 2 7 ; Bichromate of Potassium; Po- 
tassium Dichromate ; Potassic Dichromate ; Bichromate of Potash ; Red 
Chromate of Potash ; Potassic Acid Chromate ; Potassii Bichromas. 

1 part of the salt is dissolved in 10 parts of water. 

The commercial salt mag contain iron, calcium, aluminum, sulphates 
chlorides. 

43. Potassium Sulpho-Cyanide, KCyS ; Sulpho-Cyanide of Potas 
sium; Potassic Sulpho-Cyanide; Potassium Sulpho-Cyanate. 

This solution is made by dissolving 1 part of the salt in 25 parts of 
water. 

The commercial article may contain iron, sulphates, chlorides. 

44. Potassium Ferro-Cyanide, K 4 FeCy 6 ; Ferro-Cyanide of Potas- 
sium; Potassic Ferro-Cyanide ; Yellow Prussiate of Potash ; Potassii Ferro- 
cyanidum. 

This solution is made by dissolving 1 part of the crystallized salt, 
K 4 FeCy 6 ,3H 2 0, in 12 parts of water. 

45. Disodium Phosphate, Na 2 HP0 4 ; Sodium Phosphate ; Phosphate 
of Sodium ; Disodium-Hydrogen Phosphate ; Disodic-Hydric Phosphate ; 
Sodii Phosphas. 

This solution is prepared by dissolving 1 part of the crystallized salt, 
Na 2 HP0 4 + H 2 0, in 10 parts of water. 

The commercial salt may contain arsenic, iron, lead, sulphates, chlorides. 

46. Barium Chloride, BaCl 2 ; Chloride of Barium ; Baric Chloride ; 
Bar ii Chloridum. 

Dissolve 1 part of the crystallized salt, BaCl 2 + 2H 2 0, in 10 parts of 
water. 

The commercial article may contain calcium, strontium, iron, aluminum, 
silica. 

47. Calcium Hydroxide, Ca(OH) 2 ; Calcic Hydrate ; Lime Water; 
Liquor Calcis. 

This solution is best prepared in the laboratory. "Slake the lime by 
the gradua" 1 addition of 6 parts of water, then add 30 parts of water, and 
stir occasionally during half an hour. Allow the mixture to settle, decant 
the liquid and throw this away. Now add to the residue 300 parts of 
distilled water, stir well, and wait a short time for the coarser particles to 
subside, and then pour the liquid, holding the undissolved lime in suspen- 
sion, into a glass-stoppered bottle. When wanted for use, pour off the 
clear lioiiicL" — TL S. P. 



LIQUID REAGENTS. 355 

48. Magnesium Sulphate, MgS0 4 ; Sulphate of Magnesium ; Mag- 
nesic Sulphate ; Sulphate of Magnesia ; Epsom Salt; Magnesii Sulphas. 

Dissolve 1 part of the crystallized salt, MgS0 4 + 7H 2 0, in 10 parts of 
water. 

The commercial salt mag contain calcium, iron, silica, zinc, manganese, 
chlorides. 

49. Mercuric Chloride, HgCl 2 ; Bichloride of Mercury ; Perchloride 
of Mercury ; Corrosive Sublimate ; Corrosive Chloride of Mercury ; 
Hydrargyri Chloridum Corrosivum. 

Dissolve 1 part of the crystallized salt in 70 parts of water. 

The commercial salt may contain iron, lead, calcium, antimony, tin. 

50. Silver Nitrate, AgN0 3 ; Mtrate of Silver; Argentic Nitrate- 
Lunar Caustic ; Argent i Nitras. 

Dissolve 1 part of salt in 70 parts of w r ater. 

The commercial salt may contain iron, lead, copper. 

51. Lead Acetate, Pb(C 2 H 3 2 ) 2 ; Acetate of Lead; Plumbic Acetate ; 
Sugar of Lead ; Plumbi Acetas. 

Dissolve 1 part of the crystallized salt, Pb(C 2 H 3 2 ) 2 + 3 H 2 0, in 10 parts 
of water. If the solution is not clear, filter it. 

The commercial salt may contain sodium, calcium, iron, lead, copper, 
chlorides, nitrates. 

52. Ferric Chloride, Fe Cl 3 ; Perchloride of Iron ; Sesquichloride 
of Iron ; Ferri Chloridum. 

Dissolve 1 part of the solid salt, Fe 2 Cl 6 + G II 2 0, in 15 parts of water. 
The commercial article may contain ferrous chloride, aluminum, nitrates, 
sulphates. 

53. Alcohol, C 2 H 6 ; Ethyl Alcohol ; Spirits of Wine. 

The alcohol used should be the " Spirits of Wine," having a specific 
gravity of .815, and containing about 95 per cent of the spirit. This 
should be purchased ready for use. 

54. Cobaltous Nitrate, Co(N0 3 ) 2 . 

This solution is prepared by dissolving 1 part of 'he crystalline salt, 
Co(N0 3 ) 2 + 5H 2 0, in 20 parts of water. 

This solution is used merely for moistening the bead on the platinum 
wire, and should be kept in a small half-ounce bottle, as this amount will 
last a long tim 



356 APPENDIX. 



• DRY REAGENTS. 

55. Ferrous Sulphate, FeS0 4 +7H 2 0; Sulphate of Iron; Green 
Vitriol; Ferri Sulphas. 

This reagent is used in solution, 1 part of the salt to 10 parts of water ; 
but the solution oxidizes rapidly to a ferric condition, in consequence of 
which, it is best to make the solution in a test-tube, as required from time 
to time ; the proportions need not be exact. 

The dry salt also oxidizes by standing ; hence, in practice, a crystal of 
the salt is dropped into the test-tube, and a little water added ; the crystal 
is now shaken until the white coating of the ferric salt disappears, and the 
crystal is of a clear green color ; this water is now thrown out, and a fresh 
portion added ; heat is then applied to hasten the solution. 

56. Sodium Carbonate, Na 2 C0 3 ; Carbonate of Sodium ; Sodic Car- 
bonate ; Sodii Carbonas. 

This reagent is used in the form of the dry, powdered salt ; the bottle 
containing it should be kept well corked to prevent the reagent from 
absorbing the gases of the laboratory. 

The commercial salt may contain iron, aluminum, silica, calcium, lead, 
chlorides, sulphates, sulphides. 

57. Sodium Borate, Na 2 0(B 2 3 ) 2 ; Borate of Sodr;:n; Borax; Sodii 
Boras. 

This reagent is used in a dry, powdered form. 

The commercial article may contain iron, sodium, aluminum, silica, cal- 
cium, chlorides, sulphates. 

58. Sodium- Ammonium Phosphate, NaNH 4 HP0 4 .4H 2 0; Microcos- 
raic Salt; Sodii et Ammonii Phosphas. 

This is used in a dry state. 

59. i^errous Sulphide, FeS. 

The method of using this sulphide is explained in the text, Art. 167. 

60. Potassium Chlorate, KC10 3 ; Chlorate of Potassium ; Potassic 
Chlorate; Chlorate of Potash ; Potassii Chloras. 

The crystallized salt is used. 

61. Metallic Zinc, Zn. 

The granulated metal is employed. This form is obtained by pouring 
molten zinc into water. It must be absolutely free from arsenic, (See 
Art. 319.) 



REAGENTS FOR THE SIDE-TABLE. 357 



REAGENTS FOR THE SIDE-TABLE. 

These reagents are those required occasionally by the student. One 
set should be prepared and placed on a side-table, or in a cupboard conven- 
iently located, so that it is accessible to all the students in the laboratory. 
The solutions may be kept in 4-oz. bottles similar to those on the student's 
desk. The corks of all these bottles, excepting those for ether and carbon 
bisulphide, should be paraffined^ The dry salts are to be kept in convenient 
broad-mouth bottles. 

62. Carbon Bisulphide, CS 2 ; Carbon Disulphide ; Bisulphide of Car- 
bon; Carbonei Bisulphidum. 

This reagent is purchased ready for use. It is very volatile, and the 
bottle should be closed with a good chemical cork stopper. 

63. Ether, (C 2 H 5 ) 2 0; Aether; Sulphuric Ether. 

This reagent is purchased ready for use, and the bottle should be closed 
with a chemical cork stopper. 

64. Potassium Sulphate, K 2 S0 4 ; Sulphate of Potassium ; Potassic 
Sulphate ; Sulphate of Potash ; Potassii Sulphas. 

Dissolve 1 part of the crystallized salt in 12 parts of water. 

65. Potassium Ferri- Cyanide, K 3 FeCy 6 ; Ferricyanide of Potas- 
sium ; Red Prussiate of Potash. 

Dissolve 1 part of the salt in 12 parts of water. This solution will not 
keep long without undergoing decomposition. 

GG. Potassium Chromate, K 2 Cr0 4 ; Chromate of Potassium; Potas- 
sic Chromate. 

Dissolve 1 part of the salt in 10 parts of water. 

67. Potassium Cyanide, KCy; Cyanide of Potassium; Potassic 
Cyanide ; Potassii Cyanidum. 

1 part of the solid is dissolved in 4 parts of water. The poisonous 
nature of this reagent should not be forgotten. 

68. Potassium Permanganate, K Mn 4 ; Permanganate of Potas- 
sium ; Permanganate of Potash ; Potassii Permanganas. 

Dissolve 1 part of the crystallized salt in about 500 parts of water. 

69. Sodium Sulphite, Na 2 S0 3 ; Sulphite of Sodium ; Sodic Sulphite ; 
Sod ii Suiphis. 

Dissolve 1 part of the crystallized salt, Na 2 S0 3 + 7 H 2 0, in 5 parts of 
water. 



358 APFEKDIX. 

70. Calcium Sulphate, CaS0 4 ; Sulphate of Calcium; Calcic Sul- 
phate ; Calcii Sulphas. 

This solution is made by dissolving all the salt, CaS0 4 +2H 2 0, that the 
water will take up ; or, in other words, it is a saturated solution. 

71. Calcium Chloride, CaCl 2 ; Chloride of Calcium; Calcic Chloride ; 
Calcil Chlorldum. 

Dissolve 1 part of the salt, CaCl 2 + 6 H 2 0, in 8 parts of water. 

72. Stannous Chloride, SnCl 2 ; Protochloride of Tin. 

To G parts of water add 1 part of the crystallized salt, SnCl 2 + 2 H 2 ; 
then add hydrochloric acid, drop by drop, until the solution turns clear. 

73. Copper Sulphate, CuS0 4 ; Sulphate of Copper; Cupric Sulphate; 
Blue Vitriol; Blue Stone; Capri Sulphas. 

Dissolve 1 part of the crystallized salt, CuS0 4 +5H 2 0, in 8 parts of 
water. 

74. Starch Paste. This solution is made by dissolving 1 part of 
starch in 500 parts of water. In case the student desires a solution of 
starch paste and potassium iodide, he may place a little of the starch paste 
solution in a test-tube, and add a drop or two of the reagent potassium io- 
dide solution. 

75. Ammonium Molybdate, (NH 4 ) 2 Mo 4 . Dissolve 60s of the dry 
salt in 400 cc of reagent ammonia solution; add 400 cc of distilled water; 
then cautiously add 500 cc nitric acid (sp. grav. 1.4). 

GRADUATED SOLUTIONS, Etc. 

76. Clark's Soap Solution is prepared by dissolving 10s of good 
castile soap in l 1 of dilute alcohol containing about 35 per cent of the 
spirit. The dilute alcohol may be piepared from the reagent alcohol 
by mixing 368.5 CC alcohol with 631.5 CC distilled water. 

To test the soap solution a reagent solution of calcium chloride is required. 
This solution is prepared by dissolving Is of Iceland spar in hydrochloric 
acid ; the solution is then evaporated to dryness to expel any excess of 
acid, after which the residue is dissolved in l 1 of distilled water. Now if 
12 cc of the solution just formed be diluted to 70 cc and brought into a flask, 
it will require just 13 cc of the soap solution to make a permanent lather, 
provided the soap solution be of the right strength. In case the soap so- 
lution is not of the right strength, it must be made so, or allowances must 
be made when calculating the degrees of hardness of a sample of water. 
The soap solution deteriorates by standing. 



INDICATORS. 359 

77. Nessler's Solution is prepared by dissolving 13s mercuric chlo- 
ride, IIgCl 2 , in about 400 cc of distilled water; now 35s of potassium iodide, 
KI, are dissolved in (say) 200 (T of water, and these two solutions are then 
mixed. To this solution add 100s of solid potassium hydroxide, KOH, and 
when it is dissolved and the solution cool, dilute the whole with water to 
l 1 . Keep this solution in a dark, cool place, and take a portion of it in a 
small bottle for immediate use. 

Before using the solution it is necessary to " sensitize " it ; this is 
accomplished by adding slowly a saturated solution of mercuric chloride, 
with constant stirring, until the red precipitate first formed ceases to dis- 
solve. Either filter the solution or allow it to stand till the solids have all 
subsided. It is now ready for use, and should be of a light, straw-yellow 
color. This solution loses its sensitiveness by standing. 

78. A Few Graduated Solutions have been mentioned in the text ; 
as, for example, Barium Hydroxide Solution and Oxalic Acid Solution, 
p. 148; Silver Nitrate Solution, p. 107; Iodine Solution, p. 181; Ammo- 
nium Chloride Solution, p. 72. These have been sufficiently described, so 
that there is nothing to add, unless it be to note that in case these solu- 
tions prove too strong that they may be diluted to some other standard of 
strength; for example, it is evident that if l cc of the ammonium chloride 
solution be added to 99 cc of distilled water, l cc of the solution thus formed 
will correspond to .01 m s of ammonia. It is usually necessary to work, 
when estimating the ammonia of drinking-water, with this dilute solution. 
Now, if the burette used be graduated to .l cc , it is evident that by this 
means the ammonia in drinking-w r ater, etc., may be determined to .001 in ?, 
It might be well, in this connection, to call attention to the extreme accu- 
racy obtainable in titration. 

N.B. A few wordy of caution concerning the estimation of chlorine may 
be in place here. It is evident the chromate used for an indicator must 
be free from chlorine ; also, in order to have the end reaction sharp, the 
solution must be exactly neutral. 

In estimating ammonia, the water used in connection with the standard 
solution of NH 4 C1 must be free from ammonia. This may be obtained 
by taking (say) 2 1 of distilled water, and distilling until the distillate gives 
no reaction for ammonia. The water remaining in the retort is evidently 
free from ammonia. 

INDICATORS. 

Solutions of various substances are employed to indicate what is called 
" End Reactions." The method of using these indicators has been ex 



360 APPENDIX. 

plained in the text. It now remains to show how a few of these solutions 
are made. 

79. Litmus Solution is prepared by digesting for several hours 10s of 
solid litmus with 500 cc of distilled water ; allow the liquid to become clear, 
or filter it when it is ready for use, when the end reaction is to be acid; 
one portion of it may be prepared for solutions, when the end reaction is 
to be alkaline, by adding to it a few drops of acetic acid. 

80. Cochineal Solution is obtained by digesting 3s of the powder in 
250 cc of 20 per cent alcohol. This is very sensitive ; acids bleach it, alka- 
lies redden the bleached solution. 

81. Phenol-Phthalein Solution is made by dissolving 1 part of the 
solid in 100 parts of 60 per cent alcohol ; this gives a colorless solution 
which is reddened by alkalies. This red solution is bleached by acids. It 
may be used as a qualitative test for carbon dioxide. See "American Chemi- 
cal Journal," 3, 55, 232. For a paper on Lakmoid, Phenol-Phthalein, and 
other indicators, see " The Chemical News " of July 10, 1885, p. 18, and 
July 17, 1885, p. 29. 

82. A Soap-Bubble Solution is prepared thus : To about 100s of 
finely-cut best castile soap in a litre flask add nearly a litre of distilled 
water ; shake until the solution is saturated with soap ; then allow it to 
settle clear ; to two volumes of soap solution add one volume of glycerine. 

General Note. In order to lessen the first cost of equipping the 
laboratory, many of the reagents, enumerated as belonging to the student's 
desk, may be placed on the side-table. Many good laboratories are thus 
arranged. 

WORKING MATERIAL. 

The substances enumerated under this heading are arranged in the same 
order as the Elements and their compounds in the text, and none are 
repeated. It is not necessary in every case that the chemicals which fol- 
low should be chemically pure. The reagents, etc., already named are not 
given. 

83. Introduction. Galena; iron filings ; flowers of sulphur. 

84. Oxygen. Mercuric oxide; red lead; manganese dioxide (C. P.) ; 
bark charcoal; iron wire; broken watch-springs; phosphorus; zinc foil; 
pyrogallic acid. 

85. Hydrogen. Metallic sodium and potassium ; mercury ; well-watei- 
barium dioxide. 



WORKING MATERIAL. 361 

Note. For generating large quantities of hydrogen when purity is not 
especially requisite, sheet zinc may be employed; this is cut into bits, and 
to help the action along a few nails may be thrown into the generator. 

86. Nitrogen. Quicklime ; ammonium chloride ; ammonium nitrate 
(C. P.) ; copper filings; potassium nitrate; spirits of turpentine. 

87. Chlorine. Indigo solution ; sodium chloride. 

88. Bromine. Potassium bromide ; bromine. 

89. Iodine. Iodine 

90. Fluorine. Calcium fluoride ; beeswax, or paraffin. 

91. Carbon. Lampblack ; graphite ; various kinds of coal ; bone- 
black ; sugar; sodium acetate; yeast; calcium carbonate; magnesium 
ribbon ; clam shells, snail shells, corals, and other carbonates. 

92. Sulphur. Roll sulphur, iron pyrites. 

93. Silicon. As many varieties of silicon dioxide as possible. 

94. Boron. Boric acid. 

95. Phosphorus Stick phosphorus ; red phosphorus. 

When working with the metals, it is desirable to have as many ores of 
each metal as possible ; not that these ores are absolutely indispensable to 
the work in the text, but because of the advantage the student may derive 
from their examination or from working with them. 

96. The First Group Metals. Metallic silver and ores of silver; 
metallic mercury and ores of mercury ; metallic lead in its commercial 
forms, and ores of lead. 

97. Second Group Metals. Arsenic and arsenic trioxide ; antimony, 
antimony sulphide, and ores of antimony ; metallic tin in its commercial 
forms, and ores of tin ; metallic bismuth and ores of bismuth ; sheet copper, 
native copper, and ores of copper ; metallic cadmium, ores of cadmium. 

98. The Third Group Metals. Iron in its commercial form and ores 
of iron ; chrome alum or other chromium salts ; metallic aluminum and 
as many commonly occurring aluminum compounds as possible ; metallic 
nickel and ores of nickel ; cobalt ores ; manganese ores ; commercial forms 
of metallic zinc. 

99. The Fourth Group Metals. Barium dioxide, hydroxide, and as 
many barium-bearing minerals as possible ; strontium nitrate ; many cal- 
cium bearing minerals ; metallic magnesium ribbon, and many magnesium- 
bearing minerals. 

The Fifth Group 3Ietals are already provided for. 



3G2 



APPENDIX. 



GENERAL APPARATUS. 
Under this heading is included that apparatus which is of general 
utility. The teacher may need some of it for special purposes, while some 
of it is so placed that the students may have access to it at anytime 
Much of this apparatus may be used in physics also. 

100. A Becker or Troemner Balance, Fig. 23, is to he recommended 
on account of its cheapness, neatness, accuracy (sensitive to 2-e) and 
durability. By placing a small shelf or table over one pan, so that the 




Fig. 23. 

balance may play freely, it will answer well for specific gravity The 
author's students have used this balance for three years, and it is still a, 
good as new. Accompanying it is a set of weights in a polished velvet- 
hned box, with forceps, and a tray divided into compartments for the 
small weights, and covered with a glass slide. These weights were im- 
ported at a cost of §3.50 ; they run from 60s to 1* in brass and 500".=- to 
1"'S in platinum. 

101. A Pair of Counter-Poised Watch-Crystals are useful in 
weighing those substances which would attack the pans of the balance. 



GENERAL APPARATUS. 363 

102. A Weighing Flask for iodine and other volatile substances is 
desirable. 

103. A Specific Gravity Bottle of 50 cc capacity is useful in deter- 
mining the specific gravity of fluids. 

104. A Pair of Hydrometers. One for fluids lighter than water, and 
one for fluids heavier than water. 

105. A Pair of Good Centigrade Chemical Thermometers. One 
graduated from —20° to + 240°, and one from — 10° to + 360°. 

106. Graduated Flasks. One l 1 , one J 1 , and one J 1 . 

These are fitted with glass stoppers, and bear only one mark around the 
Deck. These are useful when l 1 , etc., is wanted quickly. 

107. Litre Cylinder for mixing reagent solutions. These are gradu 
ated into cc's to read up and down. 

108. Two Burettes, capacity 50 cc each; graduated to 0.1 cc . These 
ar; used in titration. 

10b A Pipette, capacity 5 CC , graduated to 0.1 cc . Used for taking out 
small quantities of liquids from bottles, etc. 

110. A Lipped Graduated Jar, capacity 100 cc , graduated to l cc . 
Used in measuring out liquids. 

111. Ure's Eudiometer. This is shown and explained in Fig. 7. 

112. Hof mann's Apparatus, as shown and explained in Fig. 3. 

113. Spectroscope. Spectroscopes are now to be had quite reason 
dbly. The needs of the school should determine the expense of the instru- 
ment purchased. 

114. Bell Jars are used in experimenting with gases. Those used in 
connection with the air-pump may be employed, or large bottles may be 
cut off at the bottom. This may be accomplished by cutting a crease 
around the bottle with a three-cornered file ; this crease is then followed 
up with a minute blow-pipe flame until the bottom cracks off. The edges 
may then be ground smooth on a sheet of emery-paper stretched on a flat 
board. 

115. Large Beakers, Funnels, Evaporating Dishes, and Ring 
Stands similar to those shown in the Frontispiece, only larger, are found 
useful in preparing solutions, reagents, etc. 

116. Retorts and Receivers, similar to those shown in Fig. 14, are 
used in distillation, etc. 



364 APPENDIX. 

117. A Liebig's Condenser is often used in connection with the 
retorts. 

118. Tall Jars are useful in experimenting with gases. 

119. An Iron Mortar and a Porcelain or a Wedgewood-Ware 
Mortar, with pestles. 

120. Assorted Glass Tubing of various sizes suitable for " hydrogen 
tones/' connections, etc. 

121. Funnel Tubes for Generators, as shown in Fig. 5. 

122. Blast-Lamp, for alcohol or gas, is useful in working glass. 

123. A Copper Oxygen Retort, for generating oxygen. An iron 
retort may be used, or a common glass generating flask will serve the 
same purpose. 

124. Mercury Trough of Porcelain. 

125. A Hydrogen Pistol may be made from a gas-pipe 1J in. in 
diameter, ^nd 6 in. long. One end is closed with a cap ; a small opening 
is drilled in for a vent, and the mouth is closed with a common cork. 

126. A Pneumatic Trough. There are many designs in use. As 
a general rule, the simpler the trough, the better. 

127. Gas Holders. Any tinsmith can make very satisfactory gas 
holders. Or they can be made from a barrel, and a cask that will go 
inside the barrel. The heads are removed; the barrel is filled with water, 
and the cask is inserted in the barrel and suitably weighted ; a stop-cock, 
for attaching rubber-hose, is inserted in the head of the cask. 

128. Chemical Corks and Rubber Stoppers of assorted sizes. 

129. Rubber Tubing of assorted sizes, for connections, etc. 

130. Rubber Gas-Bags . One of 2 gals., and one cf 1 gal. capacity. 

131. Oxyhydrogen Blow-Pipe. One form of this apparatus is 
shown in Fig. 8. Prof. Weitbrecht has constructed a cheap instrument 
from ^-in. gas fixtures. The instrument is T shaped ; into the stem of the 
T is screwed a Springfield musket cap-nipple which serves as a jet; in 
each arm of the T is a stop-cock. The hydrogen is admitted into one arm 
and the oxygen into the other. Illuminating gas may be used in place of 
hydrogen. 

132. A Furnace, known as the Fletcher Furnace, and pronded with 
bellows and a blast-jet for illuminating gas, is not expensive, and will fuse 
such metals as gold, silver, etc. 



THE LIBRARY. 365 

133. Crucibles. Hessian crucibles and plumbago crucibles are used. 
The sand, or Hessian crucible, is inexpensive, and may be bought in nests. 



THE LIBRARY. 

A reference library should be kept in the laboratory. It should be 
easy of access, and the students should be permitted to make use of any 
book at any time. Books should not be taken out of the laboratory. In 
the following list no attempt at completeness is made ; a few good books 
that are within the reach of all schools are named. Roscoe and Schor- 
lemmer's " General Treatise V will be found useful for general descriptive 
work. 

Douglas and Prescott's " Qualitative Analysis," or a standard edition 
of Fresenius's " Qualitative Analysis," will be useful in qualitative work. 

Sutton's "Volumetric Analysis" is recommended for methods of 
titration. 

Fresenius's " Quantitative Analysis " is useful, if quantitative work is 
attempted. 

Elderhorst's " Blow-Pipe Analysis " is to be used in expanding any 
work with the blow-pipe. 

Wanklyn's " Analysis of Water, Milk, and Air," may be used in case it 
is desired to do work in that direction. These books are published in 
separate volumes. 

Dana's " Mineralogy " is valuable as affording information concerning 
ores, coal, etc. 

Gore's "Electro-Metallurgy" will afford information in that direction. 

Some good work on Spectrum Analysis is desirable. Schellen, though 
popularly written, is good. Roscoe's work is more technical. 

The " U. S. Dispensatory," and the " Pharmacopoeia" are often useful. 
Bailey's " Chemist's Pocket-Book " contains many valuable data for com- 
putations, conversions, etc., etc. 

One or two chemical journals, as "The Chemical News" and the 
"American Journal of Chemistry," will serve to create an interest, by 
calling the student's attention to the present tendencies of the science. 

In response to numerous inquiries from teachers, concerning apparatus, 
etc., the author would take this occasion to say that he will gladly give 
any information in his power concerning the same; and, in case any 
school wishes aid in purchasing, that he has made arrangements with 
Messrs. Eberbach and Son, Ann Arbor, Mich., whereby any apparatus or 
chemicals necessary for this text can be supplied promptly, and at the 



366 



APPENDIX. 



lowest market price for the high grade of goods recommended. All cor- 
respondence on this subject should be addressed to the author. A priced 
list will be sent on application. 



Data for Converting Metric and English Weights and 
Measures. 

ls*= 15.43235 grains. 

1 grain = 0.0648s. 

1 lb. avoirdupois = 453.59s. 

1 oz. avoirdupois = 28.34954s. 

1 gal. U. S. = 231. cu. in. 

1 gal. Imp. = 277^ eu. in. 



1 mm 


= 0.0394 in. 


1cm 


= 0.3937 in. 


lir 


= 2.539954cm. 


1 CU. 


in. = 16.386176<*. 


Jcc 


= 0.06103 cu. in. 


11 


.= 61.02709 cu. in. 



INDEX. 



[The numbers refer to pages.] 



Acetic acid 340 

Acetylene 134 

Acid, Antimonic 249 

Boric 191 

Bromic 113 

Chloric 104 

Chlorous 104 

Citric 340 

Fuming sulphuric 174 

Hydriodic , 117 

Hydrobromic 110 

Hydrochloric 97 

Hydrocyanic 146 

Hydrofluoric 122 

Hydrofluosilicic 190 

Hypobromous 112 

Hypochlorous 101 

Hyponitrous 65 

Hypophosphorous 199 

Iodic 120 

Manganic 296 

Meta-phosphoric 202 

Meta-stannic 253 

Nitric 67 

Nitrous 66 

Nordhausen 174 

Orthophosphoric 201 

Oxalic 340 

Perchloric 105 

Permanganic 296 

Phosphoric 201 



Acid, Phosphorous e . , 200 

Prussic . . 146 

Pyrophosphoric 202 

Acids, Basicity of 168 

defined 75 

General examination for, 

204. 339 

Acid salt 217 

Acid, Selenic 179 

Selenious 179 

Sodium carbonate 333 

Stannic 253 

Sulphuric 169 

Sulphurous 168 

Tartaric 340 

Telluric 180 

Tellurous 180 

Thiosulphuric - 175 

Agate 186 

Agricola 4 

Albite 286 

Alchemy 2 

Alkali plains 327 

Alloys 211 

Alum 321 

Alumina . . . 286 

Aluminum hydroxide 287 

Aluminum, Occurrence 286 

Preparation 286 

Properties 287 

Compounds 287 



368 



INDEX. 



Aluminum, Tests 288 

sulphate 287 

Alums 287 

Amalgams 211 

Amethyst 186 

Amorphous iron ore 276 

Ammonia, Albuminoid, Estima- 
tion of 49 

Ammonia, Estimation of 72 

in drinking-water 45 

Occurrence 52 

Preparation ...... 52 

Process 332 

Properties 55 

Tests 58 

Ammonium 334 

carbonate 335 

chloride 334 

molybdate . 272 

nitrate 334 

phospho-molybdate 272 

sulphide 335 

Analysis denned 216 

of unknown substances, 337-340 

Ancients, Chemistry of. ... . 1 

Ancient copper-miners 259 

Anhydrite 314 

Anthracite 129 

Antimonic acid ... 249 

Antimony black 247, 272 

Antimony, Butter of 249 

Occurrence 247 

Preparation 247 

Properties 248 

Compounds 249 

Tests 250 

oxides 249 

trichloride 249 

trisulphide 249 

Apatite , 193 

Arabs, Chemistry of 2 



Argentite ....... 229 

Argillaceous iron ore 276 

Aristotle, Doctrines of ..... 2 

Arsenic, Occurrence 242 

Preparation 242 

Properties . . . 243 

Compounds . . 244 

Tests 246 

pentoxid j 245 

trioxide 242, 244 

Arsenious sulphide 245 

Arseniuretted hydrogen 244 

Asbestos 316 

Atomic heat 209 

theory ; 15 

weights, Determination of, 

15, 16, 152 

Atmosphere 82 

Estimation of oxygen and 

nitrogen of 85 

Impurities of 84 

Temperature of 83 

Avogadro's hypothesis 150 

Azurite 258 

Boracite 190 

Barium carbonate 311 

chloride 311 

hydroxide . . . . 310 

iodate 311 

monoxide 310 

nitrate 311 

Barium, Occurrence , .'. 310 

Preparation „ ,\ 310 

Compounds 310 

Tests 311 

sulphate 311 

Barometer , . . . 82 

Baryta, Caustic 310 

water . . 310 

Bases defined . . . . 77 



INDEX. 



369 



Basic salt 218 

Bauxite 286 

Bell metal 211 

Beryl 288 

Beryllium 302 

Bessamer process 279 

Bismuthite 255, 257 

Bismuth nitrate 257 

ochre 255 

Bismuth, Occurrence 255 

Preparation 255 

Properties 256 

Compounds 257 

Tests 257 

oxides 257 

subnitrate 257 

Binary compounds 73 

Bituminous coal 129 

Bog iron ore 276 

Bora'x 190 

Boron, Occurrence 190 

Preparation 190 

Tests 191 

Botryoidal iron ore 276 

Boyle 4 

Black lead 125 

Blanc de fard 257 

Blanc d'Espagne 257 

Blast furnace 277 

Bleaching powder . . . . . 315 

Brass 211 

Braunite •. 295 

Breithauptite 290 

Brimstone 157 

Britannia 211 

Bromic acid 113 

Bromine oxacids 112 

Bromine, Occurrence 108 

Preparation 108 

Properties 110 

Tests 110 



Bronze 211 

Brown haematite 276 

Bunsen burner 28 

Cadmium iodide 263 

Cadmium, Occurrence 262 

Preparation 262 

Properties 262 

Compounds 263 

Tests 263 

Sulphate 263 

Sulphide 263 

Caesium 336 

Calcium chloride 315 

carbonate 315 

hydroxide 314 

Occurrence 313 

Preparation 314 

Properties 314 

Compounds 314 

Tests 315 

sulphate 313, 314 

Calc spar . .313 

Carbonado 127 

Carbon bisulphide 178 

dioxide, Estimation of 148 

dioxide, Occurrence 138 

Preparation 138 

dioxide, Properties 140 

Tests 145 

hydrides 132 

monoxide, Preparation, ... 136 

Tests 138 

Occurrence 125 

Preparation 126 

Properties 126 

Tests 131 

oxides 136 

Carnallite 316, 321 

Carre, ice machine 57 

Cassiterite 251 



370 



INDEX. 



Cast iron ...*... 278 

Caustic potash 322 

soda 328 

Cavendish 5 

Celestine 312 

Cerium 304 

Chalcedony 186 

Chalk 314 

Chameleon mineral 297 

Charcoal 126 

Chemical reaction 11 

Chemism 12 

Chemistry denned 11 

Chemistry, Derivation of 1 

Chert 186 

Chili saltpetre 327 

China clay 286 

Chloric acid 104, 105 

Chlorine, Estimation of 107 

in drinking-water 45 

Occurrence 92 

Preparation 92 

Properties 95 

Tests 96 

oxacids 101 

oxides 99 

monoxide 99 

trioxide 100 

tetroxide 100 

Chlorous acid 104 

Choke damp 142 

Chrome alum 283 

Iron stone 282 

yellow , 228, 284 

Chromium hydroxide 283 

Occurrence 282 

Preparation 282 

Properties 283 

Compounds 283 

Tests 285 

oxides 283 



Chrysophrase 186 

Cinnabar 234, 235 

Citric acid 340 

Claus 270 

Coal .125, 128 

Coal analysis 147 

Cobalt, Occurrence 292 

Preparation 29S 

Properties 29S 

Compounds 293 

Tests 294 

glance 292 

Cobaltous chloride 294 

nitrate 294 

sulphate 294 

Cobalt ultramarine 294 

Coin, gold, silver, bronze 211 

Coke 129 

Columbite 307 

Combining number 14 

Combustion 27 

Spontaneous 29 

Compounds ..................... 10 

Conductivity 210 

Condy's disinfecting liquid 297 

Conglomerates 188 

Copperas 280 

Copper glance 258 

nitrate 260 

Copper, Occurrence 258 

Preparation 259 

Properties 259 

Compounds . . 260 

Tests 261 

oxides 261 

pyrites 258 

sulphate 260 

sulphides * . . 260 

Corundum 286 

Crocoisite 282 



INDEX. 



371 



Cuprite 258 

Cyanogen 145 

Dalton G 

Davy , 6 

Dialysis 187 

Diamonds 125, 126, 127 

Didymium 304 

Disodium phosphate 329 

Dog-tooth spar' 314 

Dolomite 316 

Dulong and Petit's law 209 

Dutch liquid 134 

Ekaluminum . = 303 

Egyptians, Chemistry of 1 

Elements defined 9 

Elements, Names of 17 

Classification of 219-222 

Table of 20 

Elixir Yitae 4 

Epsom salts 317 

Equations, Atomic and molecular, 155 

Meaning of 36 

Writing of 81 

Emery 286 

Erbium 305 

Etching on glass 122 

Ethylene 133 

Test for .- 134 

Experiment defined , 8 

Eat 321 

Feldspar 286 

Fermentation 139 

Eerric chloride 280 

hydroxide 280 

Ferrous chloride " 280 

sulphate 280 

sulphide 281 

Fire 27 



Fire damp 131 

Fixed alkalis 32G 

Flint 186 

Flowers of sulphur 158 

Fluorine 122 

Fluorspar 315 

Fly-powder 243 

Fool's gold 281 

Formula 18 

Franklinite 298 

Fresenius's analytical classifica- 
tion of the metals 337 

Fusible metal 211 

Galena 224, 227 

Gallium 303 

Gas carbon 129 

Geber 2 

German silver 211 

Glass . 333 

Glucinum 302 

Gold 266 

Granular iron ore 276 

Grape iron ore 276 

Graphite 125, 126, 128 

Greenockite 263 

Green vitriol 280 

Guignet's green 283 

Gunpowder 325 

Gypsum 314, 315 

Hardness of water 47, 316 

Estimation of 49 

Haematite 276 

Hausmannite 295 

Heavy spar 310, 311 

Hone stone 186 

Horn silver 229 

Hydriodic acid. 117, 118 

Hydrobromic acid 110-112 

Hydrochloric acid, Occurrence. . 97 



372 



INDEX. 



Hydrochloric acid, Preparation. . 97 

Properties 97 

Tests 99 

Hydrofluoric acid, Preparation. . 122 

Properties 122 

Tests 123 

Hydrofluosilicic acid 190 

Hydrogen arsenide 244 

Hydrogen dioxide 47, 48 

Hydrogen, Occurrence 34 

Preparation 34 

Properties 38 

Test 40 

persulphide 163 

phosphides 197 

selenide 178 

stibide 250 

sulphide, Estimation of ... . 181 

sulphide, Occurrence 160 

Preparation 161 

Properties 162 

Tests 163 

telluride 180 

Hydroxyl 71 

Hydroxylamine 70 

Hypobromous acid 112 

Hypochlorous acid 101-103 

Hyponitrites 65 

Hyponitrous acid 65 

Hypophoshorous acid 199, 200 

Iceland spar 314, 316 

Illuminating gas 135 

Indium 303 

Iodic acid 121 

Iodine, Occurrence 115 

Preparation 116 

Properties 116 

Tests 117 

oxacids 120 

oxides 120 



Iridium 270 

Iron arsenide 242 

Iron, Occurrence 275 

Preparation 276 

Properties 279 

Compounds 280 

Tests 281 

oxides , . . 280 

pyrites 281 

Jet 129 

Kaolin 286 

Kelp 115 

Kieserite 316 

Kupf er-nickel 290 

Lac sulphuris 158 

Lampblack 126 

Lanthanite 304 

Lanthanum 304 

Lapis lazuli 288 

Laughing gas 60 

Law of definite proportions 12 

of multiple proportions .... 13 

Lavoisier 6 

Lead chloride 228 

chromate 228, 284 

Lead, Occurrence . . . . 224 

Preparation 224 

Properties 226 

Compounds 227 

Tests 228 

Lepidolite 335 

Libavius 4 

Lignite 129 

Limestone 314 

Lithium 335, 336 

Liquation 251 

Lodestone 276 

Lunar caustic 232 



EsIDEX. 



373 



Magnesia 317 

Magnesite 316, 317 

Magnesium carbonate 317 

chloride 92, 317 

limestone 316 

Magnesium, Occurrence 316 

Preparation 316 

Properties 316 

Compounds 317 

Tests 317 

Magnetite 276 

Manganese acids 296 

Manganite 295 

Manganese, Occurrence 295 

Preparation 295 

Properties 295 

Compounds 296, 297 

Tests 298 

oxides 296 

sulphides 297 

Marble . . 314 

Massicot 227 

Matter 12 

Mechanical mixture 11 

Meerschaum 316 

Melting-points '. . 210 

MendelejefFs classification . .220, 221 

Mercuric chloride 235 

Mercurous chloride « . 235 

nitrate 236 

Mercury, Occurrence „ 233 

Preparation 234 

Properties 235 

Compounds 235 

Tests 237 

Red oxide of 235 

Metal, Analytical classification 

of 212, 216 

Metal defined 208 

Metals of the alkalies 320 

Metals, Salts of 216 



Metaphosphoric acid 202 

Metastannic acid „ . . . 253 

Methane 132 

Meteorites 275 

Micaceous iron ore 276 

Microcosmic salt 335 

Mispickel 242 

Molecules 149 

Molecular heat 211 

Molecular weight, Determination 

of 151, 152 

Molybdenite 272 

Molybdenum 272 

Nickel ammonium sulphate 291 

arsenide 242 

blende 290 

glance 290 

Xickel, Occurence 290 

Preparation 290 

Properties : 291 

Compounds 291 

Tests 291 

Xickel oxides 291, 293 

sulphate 291 

sulphide 291 

Xiobium 307 

Xitre 324 

Xitric acid 67-69 

Xitrites m 

in drinking-water 46 

Xitrogen chloride 106 

dioxide 61, 62 

monoxide 59-61 

Xitrogen, Occurrence, etc 50, 51 

Xitrogen oxacids 65 

oxides 58 

pentoxide 64 

tetroxide 64 

trioxide 6S 

Xitrous acid 66, 6"i 



374 



INDEX. 



Nitrous oxide 59 

Novalculite , 186 

Odontolite 288 

Oil of vitriol 172 

Opal..., 186 

Oriental amethyst 286 

emerald 286 

topaz 286 

Orpiment 242 

Orthoclase 189, 321 

Orthophosphoric acid 201 

Osmium 271 

Oxalic acid 340 

Oxidizing-flame 28 

Oxygen, Occurrence 23 

Preparation 23, 24 

Properties 25 

Tests 30 

Oxy-hydrogen blow-pipe 42 

Ozone.... 31, 32 

Palladium 269 

Paracelsus 4 

Peat 129 

Perchloric acid 105, 106 

Pewter 211 

Philosopher's stone 3 

Phlogiston 5 

Phosphate of aluminum 287 

Phosphates, Tests for 203 

Phosphoric acid 201 

Phosphorite 193 

Phosphorous acid 200, 201 

Phosphorus, Occurrence 193 

Preparation 193 

Properties 195 

Tests 196 

Phosphorus oxacids 199 

oxides 198 

pentoxide 198 



Phosphorous trioxide 198 

Pitch blende 306, 307 

Plastic sulphur 159 

Platinum 268 

Plumbago 125 

Pneumatic chemistry 5 

Potash 325 

Potassium bichromate 284 

bromide . . . . . 323 

carbonate 325 

chlorate 323 

chloride 323 

chromate 283 

chromium sulphate 283 

cyanide 325 

ferrocyanide 281 

hydroxide , 322 

iodide 323 

Potassium, Occurrence 321 

Preparation 321 

Properties 322 

Compounds 322 

Tests 326 

Potassium permanganate 297 

sulphate 323 

PriestTey 5 

Prussic acid 146 

Pyrochlor 307 

Pyrolusite 295 

Pyrophosphoric acid 202 

Quartz 186 

Quartzite 186 

Queen's metal 211 

Quicklime 314 

Realgar 242 

Red precipitate 235 

Reducing-flame 29 

Rhodium .. 271 

Rhodocrosite 295 



INDEX. 



375 



Rinmann's green 294 

Rose's metal 211 

Rubidium 336 

Ruby 286 

silver 229 

Ruthenium 270 

Rutile 305 

Safety-lamp .... 132 

Salt-cake process 330 

Saltpetre 321, 324 

Sal sodae 333 

Salts, Acid and normal 80 

denned 77 

Sand 186 

Sandstone 188 

Sapphire 286 

Scale of hardness 127 

Scheele 5 

Schweinfurth's green 245 

Scheele's green 5, 245 

Selenite 314 

Selenic acid 179 

Selenious acid 179 

Selenium dioxide. . 178 

Selenium, Occurrence 177 

Preparation 178 

Properties 178 

Tests 179 

Separation of arsenic, antimony, 

and tin 254 

of bismuth, copper, and cad- 
mium 263 

of chlorides and bromides . . 114 
of chlorides, bromides, and 

iodides 119 

of copper and bismuth 261 

of cobalt, manganese, nickel, 

and zinc 300 

of first group metals 238 



Separation of first and second 

group metals 265 

of fourth group metals 318 

of iron, chromium, and alu- 
minum 289 

of nickel and cobalt . . . 295, 302 
of second group metals .... 264 

Serpentine 189 

Siderite 276 

Silica 184, 188 

Silicates 188, 189 

of cobalt 294 

Siliceous springs 187 

Silicon fluoride 190 

hydride 189 

Silicon, Occurrence, etc. . . . 184, 185 

Silver bromide 233 

chloride 92, 232 

copper glance 229 

iodide 115 

nitrate 232 

Silver, Occurrence 228 

Preparation ' 229 

Properties 231 

Compounds 232 

Tests 233 

plating solution 232 

Skutterrudite 292 

Slaked lime 314 

Smalt 294 

Soda-ash 330 

process 331 

Soda crystals 333 

Sodium aluminate 287 

Sodium ammonium phosphate. 335 

arsenate 245 

carbonate 330 

chloride 92, 328 

hydroxide 328 

hyposulphite 329 

hypophosphite 329 



376 



LNDEX. 



Sodium nitrate .... 329 

Sodium, Occurrence 326 

Preparation . . = 327 

Properties 328 

Compounds 328 

Tests 333 

silicates 333 

thiosulphate 329 

Solder 211 

Sombrerite 193 

Soot 126 

Spathic iron ore. . .' 276 

Specific heat 209 

Spectra 303 

Specular ore 276 

Speculum metal 211 

Speiss cobalt 292, 293 

Spinelle 316 

Spirits of hartshorn 55 

Stannic acid 253 

sulphide 253 

Stannous sulphide 253 

chloride 253 

Steam, latent heat of 44 

Steatite 188 

Steel 279 

Stibnite 247, 249 

Stream tin 251 

Strontianite 312 

Strontium carbonate 312 

nitrate 312 

Strontium, Occurrence, etc. 312, 313 

Substituting power and valence. 154 

Suint 321, 325 

Sulphur acids, Tests for 176 

Sulphur dioxide, Occurrence, 

etc 164, 166 

Sulphuretted hydrogen 160 

Sulphuric acid, Estimation of . . . 182 

fuming 174 

Hydrate of 173 



Sulphuric acid, Occurrence. . . . = 16G 

Preparation 170 

Properties 172 

Tests : 173 

Sulphur, Occurrence 157 

Preparation 157 

Properties 158 

Tests 160 

Sulphur oxacids 167 

oxides ..... 164 

Sulphurous acid 168, 169 

Sulphur trioxide 167 

Superphosphate of lime 315 

Sylvite „. 321 

Symbols, Chemical 17 

Talc 316 

Tantalite 307 

Tantalum . . . . 307 

Tartar emetic 249 

Tartaric acid 340 

Tellurium acids 180 

dioxide 180 

Tellurium, Occurrence 179 

Preparation, etc 180 

Tellurium trioxide 180 

Terbium 305 

Thenard's blue 294 

Thermometers 83 

Thiosulphuric 175 

Thorite 305 

Thorium 305 

Tin foil 252 

Tin, Occurrence, etc 251-253 

Tin stone. . 251 

Titanite 305 

Titanium ] 3 305 

Titanium cyano-nitride ■....* 306 

Topaz 288 

Triphylline 335, 336 

Tripoli 18S 



INDEX. 



377 



Tungsten 271 

Turquois 287 

Type metal 211 

Ultra marine 288 

Uranium 306 

Useful problems 89 

Valence 153 

Vanadium 307 

bronze 308 

Van Helmont 4 

Vivianite 193 

Volatile alkali 320 

Volume of a gas affected by heat, 86 

by pressure 85 

Formulae for computing the, 91 

Water 40-43 

drinking, Impurities of . . . 45-47 



Water-lime 314 

Weight and density 88 

White lead 227 

Willemite 298 

Witherite 310, 311 

Wohler 6 

Wood's alloy . . 211 

Wolfram 271 

Wollaston 271 

Wollastonite 188 

Wrought iron 279 

Yttrium 304 

Yttrotantalite 307 

Zinc blende 298 

Zinc, Occurrence, etc 298-300 

Zircon 306 

Zirconium 306 



ADDENDUM. 



Argon 33 

Carbides 129, 134, 185 

Carbonyl compounds 138 

Critical pressure ...... 88 

Critical temperature 88 

Helium 22 

Krypton 33 

Liquid air 88 



Mortar 315 

Neon 33 

New elements 19 

Porcelain clay 286 

Radiant energy 7 

Radium 308 

Water-gas 136 

Xenon 33 



APR 21 1904 



